Training on Data Management and Analysis Using SPSS
Transcript of Training on Data Management and Analysis Using SPSS
Training on
Data Management and Analysis Using SPSS
Bedilu Alamirie
Addis Ababa University
Statistics Department
July, 2019
Outline1. Motivational example and Overview of SPSS
2. Modifying and Organizing Data in SPSS
3. Descriptive Statistics using SPSS
4. Testing equality of two or more population
Means
5. Nonparametric Methods using SPSS
6. Correlation and Regression Analysis
7. Analysis of Variance and Covariance using
SPSS
8. Generalized linear model using SPSS
Objectives of the training
Main Objectives of this workshop are:
• Introducing the SPSS interface
• Opening and reviewing layouts of SPSS
• Becoming familiar with menus and icons
• Manipulating data files
• Calculating descriptive statistics
• Perform in-depth analysis using real data
• Explain output produced by SPSS
Motivational Background
Why Statistics and Statistical software
important for decision making process?
Statistical Decision Making Process
Begin Here:
Identify the
Problem
Data
Organization &
Presentation of Data
Data Analysis
Interpretation
Descriptive Statistics,
Probability,
Statistical software's
Inferential
Statistics, Experience,
Theory, Literature,
Statistical software's
Software'sSTATA,SAS, R, SPSS,Excel
Information
Knowledge
Decision
Data Presentation/Summarization Methods
• Data in raw form are usually not easy to use for
decision making.
- What can you do from Eth oil enterprise, CBE,
Ethio telecom?
• Some type of organization is needed
• Summary statistics
• Table
• Graph
• The type of data summarization depends on the
type of data/variable being summarized
Example: Consider Commercial Bank of Ethiopia (CBE) data
• Raw data’s doesn’t facilitate decision making
process!
How the CBE manager will
use this data for decision making?
Types of Variable/Data
Variable/Data
Categorical/Qualitative Numerical/Quantitative
Discrete Continuous
Eg:
Marital Status
registered to vote?
Region
(Defined categories or groups) Eg:
Number of Children
Defects per hour
(Counted items)
Examples:
Weight
Height
(Measured characteristics)
8There are different statistical methods for each type!
Descriptive Statistics
Collect data
e.g., Survey
Present data
e.g., Tables and graphs
Summarize data
e.g., Sample mean = iX
n
9
Inferential Statistics
Estimation
e.g: Estimate the population mean
using the sample mean
Confidence interval
Hypothesis testing
e.g., Test the claim that the population
mean weight is 56 kg.
comparison of two or more means or
proportions
Inference is the process of drawing conclusions or making decisions about a population based on
sample results10
What is SPSS?SPSS
• Originally it was an acronym for Statistical Package for the
Social Science (SPSS) but now it stands for Statistical
Product and Service Solutions.
• It was originally launched in 1968 by SPSS Inc., and was later
acquired by IBM in 2009
• Windows based program that can be used to perform data
entry and analysis and to create tables and graphs with
simple instructions.
• Capable of handling large amounts of data and undertake a
wide range of statistical analyses relatively easily
• SPSS is updated often. The latest version is SPSS 25/6
Introduction …
• SPSS is a software for editing and analyzing all sorts of data.
• data may come from basically any source
– scientific research
– a customer database
– Google Analytics or even the server log files of a website.
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Introduction …
• SPSS can open all file formats that are commonly used for
structured data such as
– spreadsheets from MS Excel
– plain text files (.txt or .csv)
– relational (SQL) databases
– STATA and SAS etc
13
Starting SPSSYou may use any one of the following options to start SPSS.
1 Go to the Applications folder, and select SPSS from the
list of programs (or Start All Programs IBM SPSS
Statistics IBM SPSS Statistics 23).
2 Double-click SPSS shortcut icon on the desktop (if present).
SPSS welcome dialogue
SPSS Environment
• Common windows in SPSS are
– Data Editor
– Output Viewer
– Pivot Table Editor
– Chart Editor
– Syntax Editor
15
SPSS Environment
• The file extension for
– Data Editor is *.sav
– Output viewer is *.spv
– Syntax editor is *.sps
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SPSS/ Windows
• The user for SPSS/Windows is built by three primary and
distinct windows:
• Data Editor window
open at start-up and is used to enter and store data
in a spreadsheet format
• Syntax Editor windowa text editor where you compose SPSS commands
• Viewer windowresults of all statistical analyses and graphical displays
of data.
1. Data Editor window • It is the view where we see our data
• It is useful to see and manipulate the data
• It contains variables in columns and cases in rows
• It has two views:
1. Data view 2. Variable view
Click Click
columns represent variables and
rows represent cases (observations)
each row is a variable, and
each column is an attribute
associated with that
variable
A. Data View window
B. Variable View windowThis sheet contains information about the data set (to be)
stored
– name of variable, type of variable, its label and its value
B. Variable View windowName
– Variable names must be unique, and have to be less than 64 characters.
– Spaces are NOT allowed. Names are not case sensitive
Type of variables
There are different types of variables
It is displayed when clicked upper right corner of type
column
Width/Decimals• The width column allows us to specify the total number of
characters required for the column
• If numeric type of variable, it will ask to choose number of
widths and decimals (as a default the width comes 8 and
decimals of 2)
• If a qualitative data with words, it will ask you to choose
number of characteristics you wanted to add
• If date type of variable, it may ask you to choose number of
characteristics of the type of date
Decimals:
• The Decimals option allows you to specify the number of
decimal places for your variable
• It has to be less than or equal to 16
• If it is date or string variable, it will not ask you decimals
Label of the variables
Label of a variable is detailed description of the variable name
• You can specify the details of the variable
• You can write characters with spaces up to 256 characters
and may contain spaces and punctuation
Labels of values of variable• A value label is a label assigned to a particular value of a
variable
• You are most likely to use value labels for nominal orcategorical data
• It is for variables whose values are nominated
• Eg. ‘Sex’ the value can be 1. male, 2. female
• ‘Residence’ = = = = = 1. urban, 2. rural ….etc
• For continuous variables, no value is needed coding
Defining the value labels
• Click the cell in the values column as shown below
• For the value, and the label, you can put up to 60 characters.
• After defining the values click add and then click OK.
Exercise 1The following small data set consists of three variables namely,
Agecat, gender, income.
Where agecat is a categorical variable created for age.
1= ‘ Under 21 ‘ 2= ‘ 21-25’ , 3 = ‘ 26-30’
Gender: 0 = ‘Male’ and 1= ‘Female’
Income is numeric.
1. Define these variables in a data editor window
2. Enter the following data for the variables agecat, Gender and Income respectively. Your data should appear as given below.
1 1 5799
2 1 5711
3 1 3412
1 0 6393
2 0 6485
3 0 6680
3. Save the data set as exercise1.sav.
2. The Viewer window/output/
• It is displayed after any data manipulation
• Analysis result, commands are displayed in the viewer
window
• Editing of graphs is also performed in this window
2. The Viewer window/output/
3. The Syntax Editor
• It is the window in which SPSS commands can be typed and
submitted for processing.
• Commands saved in files can be opened in a syntax Editor
window for processing.
• it has *.sps extension
Opening an existing data file
Your data may already have been entered and
saved as a data file
– in SPSS having .*.sav. extension or
– a different package such as EPI info, Excel,
SAS, Stata or dBase etc.
In data editor window
• Choose the file type, and then browse and
select your file so it appears by file name.
Opening SPSS for windows
• Data also could be opened using open-
database
• Excel file, Data base file and MS access data
base could be opened
• The procedure is
Exercise 2: Open bankloan.sav from SPSS
package
Data, Transform, analysis and graphs
Data, Transform, Statistics and Graphs
• Data menu is useful to define variables and make changes to
the data file you are using.
• Transform menu is used to make changes to selected
variable(s) in the data file you are using. It includes recoding
existing variables & computing new variables.
• Statistics (Analyze) menu is useful to perform statistical
analyses such as producing Reports, calculating Descriptive
Statistics, as well as various statistical procedures such as
Regression and Correlation.
• Graphs menu lets one make various types of plots from a
given dataset.
SPSS Pull-down menus
2. Descriptive Statistics
Using SPSS
(Univariate and Bivariate)
Steps of Data Analysis
Descriptive Statistics:
1st: Univariate analysis
Examine the distribution of each variable
2nd: Bivariate analysis
Describe association between pairs of variables (mostly response with each
covariate)
Inferential Statistics:
3rd: Multiple (Multivariable) regression
• Analysis with more than one independent variables
Step 3: Use a statistical model called Regression (Linear , logistic, )
• To examine the relationship between multiple independent variables & a
dependent variable
• To gain insight into causal relationships (cause & effect)
1. Univariate Analysis
• Univariate analysis is the process of describing the sample
by examining and summarizing the distribution of each
individual variable.
• Used for all variables, regardless of level of measurement.
• Useful to make the researcher familiar with variables/data.
• It can also be used to test variables for fulfilling
assumptions.
Data Exploration
• Before doing any kind of statistical testing or model building,
examine your data using summary statistics and graphs
• Exploring data enables to know
– which values are typical
– which values are unusual
– where is it centered
– how spread out is it
– what are its extremes
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Data Exploration…
• When summarizing a quantitative variable consider
– How many observations were there?
– How many cases had missing values?
– Where is the "center" of the data?
– Where are the "benchmarks" of the data? (Quartiles, percentiles)
– How spread out is the data?
– What are the extremes of the data? (Minimum, maximum; Outliers)
– What is the "shape" of the distribution
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Descriptive Statistics (Frequency)
• Frequency
– Frequency distributions are tabular presentations of data
• show each category for a variable and
• the frequency of the category's occurrence in the data set
– Frequencies are used when you want to know how many of
something you have
– Additional statistics are also available via the Statistics button
– The Charts button is particularly useful to automatically produce
charts
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Descriptive Statistics (Frequency)…
• Frequency
– Go to
Analyze > Descriptive Statistics > Frequencies
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Descriptive Statistics (Frequency)…
• Frequency
– Clicking on buttons Statistics and Charts the following dialogue
box will appear
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Descriptive Statistics (Frequency)…
• Frequency
– Frequency for Employment Category from Employee sample data
– Majority (76%) of the employees are clerical, while little (5.7%) are
custodial.
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Descriptive Statistics (Descriptive)
• Descriptive
– The descriptive procedure produces summary measures for numeric
variables
– It produces measures of center, spread and shape & size
– Go to
Analyze > Descriptive Statistics > Descriptives…
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Descriptive Statistics (Descriptive)…
• Descriptive
– Click Options button to get what measures to get
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Descriptive Statistics (Descriptive)…
• Descriptive
– Use Employee sample data to describe the salary variable
– The average salary of employees is 34419.57 dollars with 17075.66 dollars
spread in standard deviation. Also the minimum salary paid is 15750 dollars
while the maximum is 135000 dollars.
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Descriptive Statistics (Explore)
• Explore
– It produces detailed univariate statistics and graphs for numeric scale
variables
– It can also be used to assess the normality of a numeric scale
variable with special inferential statistics and detailed diagnostic
plots
– It produce results by controlling for a particular categorical variable
52
Descriptive Statistics (Explore)…
• Explore
– Got to
Analyze > Descriptive Statistics > Explore
53
Descriptive Statistics (Explore)…
• Explore
– Use Employee sample data to display detailed univariate statistics for
salary
– The missing and non-missing cases in count and percent are
displayed.
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Descriptive Statistics (Explore)…
• Explore…
– The mean salary of clerical employees is 27838.54 dollars with a standard deviation
of 7567.995 dollars; 50% of clerical employees get at most 26550 dollars.
»
55
• salary of clerical workers has
asymmetric shape and a
leptokurtic size.
Descriptive Statistics (Crosstabs)
• Crosstabs
– Frequency table describes a single categorical variable
– Cross tabulation describes the relationship between two categorical
variables
• It can be called as two way table, contingency table or crosstabs
– Go to
Analyze > Descriptive Statistics >Crosstabs...
» 56
Descriptive Statistics (Crosstabs)…
• Crosstabs…
– Use Employee sample data to display detailed univariate statistics for
salary
»
57
Descriptive Statistics (Crosstabs)…
• Crosstabs…
– Use Employee sample data to display detailed univariate statistics for
salary
– The total number of female clerical employees are 206, while male
clerical are 157.
»
58
Descriptive Statistics (Crosstabs)…
• Crosstabs…
– Remark: you can create a higher order table by entering in “Layer”
box
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Click next
until you
complete the
categorical
variables to
be used
Descriptive Statistics (Ratio)
• Ratio
– The Ratio Statistics procedure provides a comprehensive list of summary
statistics for describing the ratio between two scale variables.
– It is helpful to calculate range, average absolute deviation, median-centered
coefficient of variation and mean-centered coefficient of variation.
– Go to
Analyze > Descriptive Statistics >Ratio...
60
Descriptive Statistics (Ratio)…
• Ratio…
– Use Employee sample data to display ratio of beginning salary
(salbegin) and current salary (salary)
– v
61Click on Statistics
Descriptive Statistics (Ratio)…
• Ratio…
» 62
Descriptive Statistics (P-P plots)
• P-P Plots
– Useful to check whether a variable under consideration follows a
certain distribution, eg: Normal
– Go to
Analyze > Descriptive Statistics >P-P Plots...
63
Descriptive Statistics (P-P plots) …
• P-P Plots
– Use Employee sample data to test normality of current salary (salary)
»
64
Select the type of
distribution to be
checked
Descriptive Statistics (P-P plots) …
• P-P Plots
– Use Employee sample data to test normality of current salary (salary)
»
65
Descriptive Statistics (Q-Q plots)
• Q-Q Plots
– Useful to check whether a variable under consideration follows a
certain distribution, eg: Normal
– Go to
Analyze > Descriptive Statistics >Q-Q Plots...
66
Descriptive Statistics (Q-Q plots) …
• Q-Q Plots…
– Useful to check whether a variable under consideration follows a
certain distribution, eg: Normal
»
67
Select the type of
distribution to be
checked
Descriptive Statistics (Q-Q plots) …
• Q-Q Plots…
– Useful to check whether a variable under consideration follows a
certain distribution, eg: Normal
»
68
Descriptive Statistics (Graphs)
• Graphs
– SPSS provides a wide variety of charts(graphs) to choose from such as
• Bar chart
• Pie chart
• Histogram
• Boxplots and
• Scatter plots
– There are three options to produce graphs
• Chart Builder
• Graph board Template Chooser and
• Legacy Dialogs 69
Descriptive Statistics (Graphs) …
• Chart Builder
– Go to
Graph > Chart builder >OK
»
70Click Ok
Choose chart
type
Descriptive Statistics (Graphs)…
• Chart Builder…
– Use Employee sample data to construct bar chart for Job category (jobcat)
»
71
Click OkSelect the statistic to
be displayed
Descriptive Statistics (Graphs) …
• Chart Builder
– Go to
Graph > Graphboard Template Chooser…
72
Descriptive Statistics (Graphs) …
• Chart Builder…
– Use Employee sample data to construct bar chart for Job category (jobcat)
73
Descriptive Statistics (Graphs) …
• Legacy Dialogs
– Go to
Graphs> Legacy Dialogs>Bar/3-D Bar/Line/Area/Pie/ etc
74
Descriptive Statistics (Graphs) …
• Multiple Bar Chart
– Use Employee sample data to construct multiple bar chart for current salary
(salary) by Gender(gender)
75
Select
Clustered
Click Define
1
2
Descriptive Statistics (Graphs) …
• Multiple Bar Chart
– Use Employee sample data to construct multiple bar chart for current salary
(salary) by Gender(gender)
76
Sel
ect
wh
at b
ars
rep
rese
nt
Click
Change
statistic
1 2
3
Descriptive Statistics (Graphs) …
• Multiple Bar Chart
– Use Employee sample data to construct multiple bar chart for current salary
(salary) by Gender(gender) for job category(jobcat)
77
Click Ok
Descriptive Statistics (Graphs) …
• Stacked Bar Chart
– Use Employee sample data to construct multiple bar chart for current salary
(salary) by Gender(gender) for job category(jobcat)
78
Sel
ect
wh
at b
ars
rep
rese
nt
Click
Change
statistic
1 2
3
Descriptive Statistics (Graphs) …
• Stacked Bar Chart
– Use Employee sample data to construct multiple bar chart for current salary
(salary) by Gender(gender) for job category(jobcat)
79
Descriptive Statistics (Graphs) …
• Histogram
– Histograms are used for visualizing quantitative data.
– Go to
Graphs>Legacy Dialogs>Histogram…
80
Descriptive Statistics (Graphs) …
• Histogram
– Use Employee sample data to construct histogram for current salary (salary)
81
Descriptive Statistics (Graphs) …
• Box Plot
– Boxplots are useful to check variability, observe outliers, etc
– They are also useful way of comparing two or more datasets
– Go to
Graphs>Legacy Dialogs>Boxplot
82
1
2
Descriptive Statistics (Graphs) …
• Box Plot…
– Use Employee sample data to construct histogram for current salary (salary)
by employment category (jobcat)
83
Descriptive Statistics (Graphs) …
• Box Plot…
84
Inferential Statistics
• Statistical inference refers to making generalizations about populations
based on samples of those populations
• Two basic issues in statistical inference: estimation and hypothesis
testing
• Inferential procedures can be either parametric or non-parametric
• Parametric: Assumptions about the shape of the distributions of the
population are mandatory.
– Examples: t test, z test, ANOVA, etc.
• Non-parametric: These do not require any assumption on the shape of
the distribution.
– Examples: Chi-square, the Mann-Whitney U , the Wilcoxon test, etc.85
Inferential Statistics
• One sample t test
– A one-sample test can be used to compare a sample mean to a given
value.
– Assumptions
• Test variable that is continuous (i.e., interval or ratio level)
• Observations on the test variable are independent
• Random sample of data from the population
• Normal distribution (approximately) of the sample and population on the
test variable
• No outliers86
0 0 1 0: :H vs H
Inferential Statistics…
• One sample t test …
– Use Employee sample data to test mean current salary (salary) is different
from 34000 dollars
– Go to
Analyze >Compare Means >One-Sample T Test...
87
Inferential Statistics…
• One sample t test …
88
Select the
variable to
be tested
1
3
2Specify the
claim
4Specify the
level of
confidence
5
6
Inferential Statistics…
• One sample t test …
• The mean salary of employees is not different from $34000
89
Inferential Statistics…
• Two sample paired t test
– This compares the differences between pairs of readings for two
related samples
– The two means typically represent two different times (e.g., pre-test
and post-test with an intervention between the two time points) or
two different but related conditions or units (e.g., left and right ears,
twins).
– The purpose of the test is to determine whether there is statistical
evidence that the mean difference between paired observations on a
particular outcome is significantly different from zero.
90
Inferential Statistics…
• Two sample paired t test…
– Assumptions
• Dependent variable that is continuous (i.e., interval or ratio level)
• The paired measurements must be recorded in two separate
variables
• Related samples/groups (i.e., dependent observations)
• Random sample of data from the population
• Normal distribution (approximately) of the difference between
the paired values
• No outliers in the difference between the two related groups
91
Inferential Statistics…
• Two sample paired t test
– To run paired t test go to
Analyze> Compare Means > Paired-Samples T Test
92
Inferential Statistics…
• Two sample paired t test
– From Employee sample data set assuming normality for the
difference for beginning salary (salbegin) and current salary (salary).
Conduct paired t test.
93
1 2
3
45
6
Inferential Statistics…
• Two sample paired t test…
• There is a significant difference between beginning salary and current salary of
employees.94
Inferential Statistics…
• Two sample Independent t test
– The Independent Samples t Test compares the means of two
independent groups in order to determine whether there is statistical
evidence that the associated population means are significantly
different.
– The purpose of the test is to determine whether there is statistical
evidence that the mean difference between two groups of
observations on a particular outcome is significantly different from
zero.
• Compare salary of male and female
95
Inferential Statistics…
• Two sample Independent t test…
– Assumptions
• Dependent variable that is continuous (i.e., interval or ratio level)
• Independent variable that is categorical (i.e., two or more groups)
• Cases that have values on both the dependent and independent variables
• Independent samples/groups (i.e., independence of observations)
• Random sample of data from the population
• Normal distribution (approximately) of the dependent variable for each
group
• Homogeneity of variances (i.e., variances approximately equal across
groups)
• No outliers96
Inferential Statistics…
• Two sample Independent t test…
– To run two sample independent t test go to
Analyze> Compare Means > Independent Samples T Test
97
Inferential Statistics…
• Two sample Independent t test…
– From Employee sample data set assuming normality current salary
(salary). Conduct whether salary for males is different from females.
98
12
3
4
5
6
7
Inferential Statistics…
• Two sample Independent t test…
• Consider two cases
– Equal variance
– Unequal variance 99
The mean salary of males is
different from females
The variability of salary for
males and females is not equal
Inferential Statistics…
• One way ANOVA
– Use when there are more than two group means which are
independent
– The variables used in this test are known as:
• Dependent variable
• Independent variable (also known as the grouping variable, or factor)
– The total variance of all samples will be calculated; portion can be
accounted by known and unknown causes.
100
Inferential Statistics…
• One way ANOVA…
– Assumptions
• Dependent variable that is continuous (i.e., interval or ratio level)
• Independent variable that is categorical (i.e., two or more groups)
• Cases that have values on both the dependent and independent variables
• Independent samples/groups (i.e., independence of observations)
• Random sample of data from the population
• Normal distribution (approximately) of the dependent variable for each
group (i.e., for each level of the factor)
• Homogeneity of variances (i.e., variances approximately equal across
groups)
• No outliers101
Inferential Statistics…
• One way ANOVA…
– To run one way ANOVA go to
Analyze> Compare Means > One-Way ANOVA...
102
Inferential Statistics…
• One way ANOVA…
– From Employee sample data set assuming normality current salary (salary).
Conduct whether salary different at least between two Employment
categories (jobcat)
103
1
2
3
4
56
Inferential Statistics…
• One way ANOVA…
104There is at least difference in the salary of two Employment
categories
Inferential Statistics…
• Chi Square Tests of independence
– Used to test variables that have nominal data
– It doesn’t recognize any quantitative distinction among categories
– Test to see whether a relationship (association) exists between two
nominal variables
– Analogues to bivariate correlation
– Compares expected and observed counts in each category
105
Inferential Statistics…
• Chi Square Tests of independence
– To perform chi-square test of association go to
Analyze> Nonparametric Tests> Legacy Dialogs> Chi-square…
106
Inferential Statistics…
• Chi Square Tests of independence
– Use Employee sample data to test association between Employment
category (jobcat) and minority classification (minority)
107
There is a association between
jobcat and minority.
Inferential Statistics…
• Wilcoxon Signed-Ranks Test
– It is a non-parametric equivalent test for paired t test
– Used when the assumption of normality is violated
– It can also be used on ordinal variables -although ties may be a real
issue for Likert items
108
Inferential Statistics…
• Wilcoxon Signed-Ranks Test
– To perform Wilcoxon Signed-Rank test go to
Analyze> Nonparametric Tests> Legacy Dialogs> 2 Related Samples…
109
Inferential Statistics…
• Wilcoxon Signed-Ranks Test
– Use Employee sample data to conduct current salary (salary) and
beginning salary (salbegin) are same
110
1 2
3
4
Inferential Statistics…
• Wilcoxon Signed-Ranks Test
111
There is a statistically
significant difference on the
beginning and current salary
Displays the number of -, +,
0 difference
Inferential Statistics…
• Mann-Whitney U Test
– It is a nonparametric test equivalent to two sample independent t test
– The assumptions of the Mann-Whitney U test are
• The variable of interest is continuous (not discrete). The measurement
scale is at least ordinal
• The probability distributions of the two populations are identical, except
for location
• The two samples are independent
• Both samples are simple random samples from their respective
populations. Each individual in the population has an equal probability
of being selected in the sample
• Can be called Wilcoxon Test not Wilcoxon Signed Rank test112
Inferential Statistics…
• Mann-Whitney U Test
– To run Mann-Whitney test go to
Analyze> Nonparametric Tests> Legacy Dialogs> 2 Independent Samples…
113
Inferential Statistics…
• Mann-Whitney U Test
– Use Employee sample data to test equality of salary for minority
classification
114
1
2
3
4
5
6
Inferential Statistics…
• Mann-Whitney Test…
115
There is a significant difference in the current
salary of employees based on employment
category
Inferential Statistics…
• Kruskal-Wallis Test
– The Kruskal-Wallis test is an alternative for a one-way ANOVA if
the assumptions of the latter are violated
– It is a rank based nonparametric test
– It is an extension of Mann-Whitney Test
– To run Kruskal-Wallis test go to
Analyze> Nonparametric Tests> Legacy
Dialogs> K Independent Samples…
116
Inferential Statistics…
• Kruskal-Wallis Test…
117
Inferential Statistics…
• Kruskal-Wallis Test…
– Use Employee sample data to test for difference in current salary
based on Employment category
118
1
2
3
4
5
6
Inferential Statistics…
• Kruskal-Wallis Test…
119
There is a difference at least between two
employment categories on their current
salary
Inferential Statistics…
• Correlation Analysis
– Measures the strength and direction of linear relationship between
pairs of variables
– To run bivariate Pearson correlation go to
Analyze> Correlate> Bivariate
120
Inferential Statistics…
• Correlation Analysis
– Use Employee sample data to run bivariate correlation between
beginning salary (salbeg) and current salary (salary)
121
There is a strong linear relationship
between beginning salary and current
slary.
Inferential Statistics…
• Partial correlation Analysis
– Partial correlation is a measure of the strength and direction of a
linear relationship between two continuous variables whilst
controlling for the effect of one or more other continuous variables
• Example:
– A linear relationship between ice cream sales and price, whilst
controlling for daily temperature
– relationship between 10,000 m running performance and VO2max
but you would like to know if this relationship is affected by wind
speed and humidity
122
Inferential Statistics…
• Partial correlation Analysis
– Assumptions
• There is one (dependent) variable and one (independent) variable
and these are both measured on a continuous scale (i.e., they are
measured on an interval or ratio scale).
• There are one or more control variables, also known as covariates
(i.e., control variables are just variables that you are using to adjust the
relationship between the other two variables; dependent and
independent
• There needs to be a linear relationship between all pairwise variables
• There should be no significant outliers
• variables should be approximately normally distributed 123
Inferential Statistics…
• Partial correlation Analysis
– To run partial correlation go to
Analyze> Correlate> Partial…
124
Inferential Statistics…
• Partial correlation Analysis
– Use job_satisfaction data to partial correlation
125
1
2
3
Inferential Statistics…
• Partial correlation Analysis
126
Correlation between Outcome of job performance and outcome
of motivation test controlling for the effect of outcome of
social support
Inferential Statistics…
• Linear Regression Analysis
– Used when we want to predict the value of a variable based on the
value of another variable.
– The variable we want to predict is called the dependent variable (or
sometimes, the outcome variable).
– The variable we are using to predict the other variable's value is
called the independent variable (or sometimes, the predictor
variable).
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Inferential Statistics…
• Linear Regression Analysis
– Assumptions
• Dependent variables should be measured at the continuous level (i.e., either
interval or ratio variables).
• There needs to be a linear relationship between the dependent and independent
variables.
• There should be no significant outliers.
• Observations should be independent, check using the Durbin-Watson statistic,
which is a simple test to run using SPSS Statistics.
• Data should be homoscedastic
• The residuals (errors) of the regression line are approximately normally
distributed
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Inferential Statistics…
• Linear Regression Analysis
– To run regression analysis go to
Analyze> Regression> Linear…
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Inferential Statistics…
• Linear Regression Analysis
– A company wants to know how job performance (perf) relates to IQ (iq),
motivation (mot) and social support (soc).
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2
3
Inferential Statistics…
• Linear Regression Analysis
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65.4% of the total variation in performance is
explained by IQ, Mot, and Soc
This shows overall significance
All predictors are
significant
A unit increase in IQ
will have an increase in
performance by 0.265
units
Inferential Statistics…
• Binary Logistic Regression Analysis
– Predicts the probability that an observation falls into one of two
categories of a dichotomous dependent variable based on one or
more independent variables
– Suppose that we are interested in the factors that influence whether a
political candidate wins an election.
• The outcome (response) variable is binary (0/1); win or
lose.
• The predictor variables of interest are
– the amount of money spent on the campaign,
– the amount of time spent campaigning negatively and
– whether or not the candidate is an incumbent.
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Inferential Statistics…
• Binary Logistic Regression Analysis
– Assumptions
• dependent variable should be measured on a dichotomous scale
• one or more independent variables, which can be either
continuous or categorical
• independence of observations and the dependent variable should
have mutually exclusive and exhaustive categories
• a linear relationship between any continuous independent
variables and the logit transformation of the dependent variable.
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Inferential Statistics…
• Binary Logistic Regression Analysis…
– To run binary logistic regression go to
Analyze >Regression >Binary Logistic…
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Inferential Statistics…
• Binary Logistic Regression Analysis…
– Use job_performance data to fit logistic regression
– Convert perf variable into categorical (perfcat)based on a cutoff point 78
135
78,
78,
perf badperfcat
perf good
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2
3
4
5
9
7
8
6
Inferential Statistics…
• Binary Logistic Regression Analysis…
136
The model fits well
the explained variation in the dependent
variable based on our model ranges from
24.0% to 33.0%
Inferential Statistics…
Binary Logistic Regression Analysis…
137
The model predicts
76.70% correctly
Statistical significance for each of the independent variables
A unit increase in soc score will increase the odds of getting a good
performance evaluation by a factor of 1.038
Inferential Statistics…
Multinomial Logistic Regression Analysis
• Used to predict a nominal dependent variable given one or more
independent variables
• An extension of binary logistic regression
• Entering high school students make program choices among general
program, vocational program and academic program.
– Their choice might be modeled using their writing score and their social
economic status.
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Inferential Statistics…
Multinomial Logistic Regression Analysis…
• Assumptions
– dependent variable should be measured at the nominal level
– have one or more independent variables that are continuous, ordinal or
nominal
– have independence of observations and the dependent variable should have
mutually exclusive and exhaustive categories
– There should be no multicollinearity
– There needs to be a linear relationship between any continuous independent
variables and the logit transformation of the dependent variable.
– There should be no outliers, high leverage values or highly influential points
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Inferential Statistics…
Multinomial Logistic Regression Analysis…
• To run multinomial logistic regression go to
Analyze >Regression >Multinomial
Logistic…
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Inferential Statistics…
Multinomial Logistic Regression Analysis…
• Entering high school students make program choices among
general program, vocational program and academic program.
Their choice might be modeled using their writing score and their
social economic status.
• Use multidemo data
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Inferential Statistics…
Multinomial Logistic Regression Analysis…
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2 3
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5
8
6
7
Inferential Statistics…
Multinomial Logistic Regression Analysis…
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Descriptive percentage for categorical variables
Model improves by adding ses and write for
explaining type of type of program admitted
Proportion of variation explained
Inferential Statistics…
Multinomial Logistic Regression Analysis…
144
• Tests for the overall effect of ses
and write
• The effects are statistically
significant
Inferential Statistics…
Multinomial Logistic Regression Analysis…
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Inferential Statistics…
Multinomial Logistic Regression Analysis…
• A one-unit increase in the variable write is associated with a 0.058
decrease in the relative log odds of being in general program versus
academic program
• A one-unit increase in the variable write is associated with a .1136
decrease in the relative log odds of being in vocation program versus
academic program.
• The relative log odds of being in general program versus in academic
program will increase by 1.163 if moving from the highest level of
ses (ses = 3) to the lowest level of ses (ses = 1).
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