Sampling - MBA -B -Section
-
Upload
wahid-rokadiya -
Category
Documents
-
view
221 -
download
0
Transcript of Sampling - MBA -B -Section
-
8/7/2019 Sampling - MBA -B -Section
1/46
Business Mathematics & Analytics
Module 5Sampling
-
8/7/2019 Sampling - MBA -B -Section
2/46
"The secret of success is to know something
nobody else knows. "
Aristotle Onassis
-
8/7/2019 Sampling - MBA -B -Section
3/46
How will you differentiate?
Data
Information
-
8/7/2019 Sampling - MBA -B -Section
4/46
Uncertainty
I dont know
if we
should
offer on-site
child care?
-
8/7/2019 Sampling - MBA -B -Section
5/46
Information Reduces uncertainty
Helps focus decision making
Research is
a systematic Inquiry whose objective is to provide informationto solve managerial problems
-
8/7/2019 Sampling - MBA -B -Section
6/46
Follow the Yellow Brick Road ofFollow the Yellow Brick Road of
the Research Processthe Research Process
Problem Discovery
and Definition
ResearchDesign
Sampling
Data
Gathering
Data Processing
and Analysis
Conclusions and
Report
Discovery and
Definition
and so on
-
8/7/2019 Sampling - MBA -B -Section
7/46
SamplingT
erminology Population or universe
Population element
Census
Sample
Sampling
-
8/7/2019 Sampling - MBA -B -Section
8/46
Population Any complete group
People
Sales territories
Stores
-
8/7/2019 Sampling - MBA -B -Section
9/46
Census Investigation of all individual elements that
make up a population
-
8/7/2019 Sampling - MBA -B -Section
10/46
POPULATIONPOPULATION
SAMPLESAMPLESample:S
ample: subsetsubsetof a larger populationof a larger population..
Selecting a Sample
-
8/7/2019 Sampling - MBA -B -Section
11/46
SamplingSampling is the process of selecting part of a
larger group of participants with the intent
of generalizing from the smaller group.
-
8/7/2019 Sampling - MBA -B -Section
12/46
Theories of sampling
The law of inertia of large numbers
The law of statistical regularity
The law of persistence
The law of optimization
T
he law of validity
-
8/7/2019 Sampling - MBA -B -Section
13/46
Why sample?
1.Budget and Time constraints
2.Complete population inaccessible
3. Accurate and reliable results
4. Whenever destruction of test units is
involved.
-
8/7/2019 Sampling - MBA -B -Section
14/46
Define the target population
Select a sampling frame
Conduct fieldwork
Determine if a probability or nonprobability
sampling method will be chosen
Plan procedure
for selecting sampling units
Determine sample size
Select actual sampling units
Stages in the
Selection
of a Sample
-
8/7/2019 Sampling - MBA -B -Section
15/46
Two Major Categories of
Sampling Probability sampling
Known, nonzero probability for every
element
Nonprobability sampling (Purposive
method)
Probability of selecting any particularmember is unknown
-
8/7/2019 Sampling - MBA -B -Section
16/46
Nonprobability Sampling Convenience
Judgment
Quota
Snowball
-
8/7/2019 Sampling - MBA -B -Section
17/46
Convenience Sampling
Also called haphazard or accidental
sampling
The sampling procedure of obtaining the
people or units that are most conveniently
available
-
8/7/2019 Sampling - MBA -B -Section
18/46
Convenience
Advantages
No need for list of
populaiton
Disadvantages
Variability and bias of
estimates cannot be
measured or controlled. Projecting data beyond
sample is inappropriate.
-
8/7/2019 Sampling - MBA -B -Section
19/46
Judgment Sampling Also called purposive sampling
An experienced individual selects the
sample based on his or her judgment about
some appropriate characteristics required of
the sample member
-
8/7/2019 Sampling - MBA -B -Section
20/46
Judgment
Advantages
Useful for certain types of
forecasting
Sample guaranteed to meeta specific objective.
Disadvantages
Bias due to experts beliefs
may make sample
unrepresentative. Projecting data beyond
sample is inappropriate.
-
8/7/2019 Sampling - MBA -B -Section
21/46
Quota Sampling Ensures that the various subgroups in a
population are represented on pertinent
sample characteristics
To the exact extent that the investigators
desire
It should not be confused with stratifiedsampling.
-
8/7/2019 Sampling - MBA -B -Section
22/46
Quota
Advantages
Introduces some
stratification of population
Requires no list ofpopulation
Disadvantages
Introduces bias in
researchers classification of
subjects Non random selection
within classes means error
from population cannot be
estimated Projecting data beyond
sample is inappropriate.
-
8/7/2019 Sampling - MBA -B -Section
23/46
Snowball Sampling A variety of procedures
Initial respondents are selected by
probability methods
Additional respondents are obtained from
information provided by the initial
respondents
-
8/7/2019 Sampling - MBA -B -Section
24/46
Snowball
Advantages
Useful in locating members
of rare populations.
Disadvantages
High bias because sample
units are not independent
Projecting data beyondsample is inappropriate.
-
8/7/2019 Sampling - MBA -B -Section
25/46
Nonprobability SamplingReasons to use
Procedure satisfactorily meets the sampling
objectives
Lower Cost
Limited Time
Not as much human error as selecting a
completely random sample
Total list population not available
-
8/7/2019 Sampling - MBA -B -Section
26/46
Probability Sampling Simple random sample
Systematic sample
Stratified sample
Cluster sample
Multistage Multiphase
Area sampling
-
8/7/2019 Sampling - MBA -B -Section
27/46
Simple Random Sampling A sampling procedure that ensures that each
element in the population will have an equal
chance of being included in the sample.
-
8/7/2019 Sampling - MBA -B -Section
28/46
-
8/7/2019 Sampling - MBA -B -Section
29/46
-
8/7/2019 Sampling - MBA -B -Section
30/46
From a college of 2000 students, select a
sample of 20 students without replacement.
-
8/7/2019 Sampling - MBA -B -Section
31/46
Simple random
Advantages
Only minimal advance
knowledge of population
needed Easy to analyze data and
compute error
Disadvantages
Requires sampling frame to
work from
Does not use knowledge ofpopulation that researcher
may have
Larger errors for same
sample size than withstratified sampling
Respondents may be widely
dispersed
H
ence cost may be higher
-
8/7/2019 Sampling - MBA -B -Section
32/46
Systematic Sampling A simple process
Every nth name from the list will be drawn
-
8/7/2019 Sampling - MBA -B -Section
33/46
Systematic
Advantages
Simple to draw sample
Easy to check
Disadvantages
If sampling interval is
related to a periodic
ordering of the population,may introduce increased
variability
-
8/7/2019 Sampling - MBA -B -Section
34/46
Stratified Sampling Subsamples are drawn within different
strata
Each stratum is more or less equal on some
characteristic
Do not confuse with quota sample
-
8/7/2019 Sampling - MBA -B -Section
35/46
Stratified
Advantages
Assures representation of all
groups in sample
Characteristics of eachstratum can be estimated
and comparisons made
Reduces variability for
same sample size
Disadvantages
Requires accurate
information on proportion in
each stratum If stratified lists are not
already available, they can
be costly to prepare.
-
8/7/2019 Sampling - MBA -B -Section
36/46
Cluster Sampling The purpose of cluster sampling is to
sample economically while retaining the
characteristics of a probability sample.
The primary sampling unit is no longer the
individual element in the population
The primary sampling unit is a larger clusterof elements located in proximity to one
another
-
8/7/2019 Sampling - MBA -B -Section
37/46
Cluster
Advantages
If clusters geographically
defined
Yields lowest field cost
Requires listing of all
clusters but of individuals
only within clusters
Can estimate characteristicsof clusters as well as of
population
Disadvantages
Larger error for comparable
size than other probability
samples Researcher must be able to
assign population members
to unique cluster or else
duplication or omission ofindividual results
-
8/7/2019 Sampling - MBA -B -Section
38/46
-
8/7/2019 Sampling - MBA -B -Section
39/46
COMPLETELY
CERTAIN
ABSOLUTE
AMBIGUITY
CAUSAL,
COMPARATIVE,
ASSOCIATIONAL,
OR DESCRIPTIVE
EXPLORATORY
Uncertainty Influences
The Type OfResearch
-
8/7/2019 Sampling - MBA -B -Section
40/46
Exploratory Research Descriptive Research Causal Research
(Unaware of Problem) (Aware of Problem) (Problem Clearly Defined)
Our sales are declining and What kind of people are buying Will buyers purchase more of
we dont know why. our product? Who buys our our products in a new package?
competitors product?
Would people be interested Which of two advertising
in our new product idea?
campaigns is more effective?
Degree of Problem Definition
-
8/7/2019 Sampling - MBA -B -Section
41/46
Descriptive Research
Examples
WeightWatchersaverage customer
W
oman about 40years old
Household incomeof about $50,000
At least some
college educationTrying to juggle
children and a job
-
8/7/2019 Sampling - MBA -B -Section
42/46
Causal Study
Studying the effects of a training program onemployee performance
-
8/7/2019 Sampling - MBA -B -Section
43/46
Sampling errors Difference between
the results of studying a sample and
inferring a result about the population
and the results of the census of the whole
population
-
8/7/2019 Sampling - MBA -B -Section
44/46
Causes of sampling errors
Unrepresentative sample
Small sample size
Indeterminacy in principle
-
8/7/2019 Sampling - MBA -B -Section
45/46
Non sampling errors Non sampling errors are errors that occur in
acquiring, recording or tabulating statistical
data that cannot be ascribed to samplingerror.
They may arise in either a census or a
sample. Two types Systematic (Biased) and
Unsystematic
-
8/7/2019 Sampling - MBA -B -Section
46/46
T
hank you