SPSS 202: Data Management by SPSS (Workshop)

Dr. Daisy DaiDepartment of Medical Research

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Log in SPSS

• CMH offers server version SPSS 18. Any employee can log in SPSS from your employee account.

• Go to https://remoteaccess.cmh.edu

• Enter cmh user name and password.

• Click SPSS 18 icon.

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SPSS Data Entry

• SPSS data can be entered manually. – The format is ready for analysis.

• SAS, Excel, txt, etc. data can be easily imported to SPSS.

• SPSS data files are saved as “SPSS data document (.sav)”.

• SPSS output files are saved as “SPSS viewer document (.spv)”.

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SPSS Data Entry

• SPSS has a few unique features in data entry. – Categorical variables need to be coded. For instance, code

male as 1 and female as 0 or vice versa.– When you have two treatments, test and control, please

use 1 for test and 0 for control. – Categorical variables that are not coded in other sourced

data files will not be imported or analyzed properly in SPSS.

– Continuous variables don’t need coding. – Missing values needs to be defined in “variable view”

page.

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Example: CDC Survey Data

• An allergy survey was conducted in 2005 and 2006 to children more than 1 year old.

• Two data sets, allergy questionnaire and demographic information, are saved in sas export format.

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CDC Survey Data

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Tasks

• Import these two SAS data files (demo_d.xpt, agq_d.xpt) to SPSS and save them as SPSS data file.

• Sort each data set by study ID.• Merge allergy variables and demographic

variables.• Save new data set as SPSS data file.

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Task 1: Import Data

• We need to import two data sets to SPSS.– Allergy qustionaire: aqq_d.xpt (xpt is sas Xport Tranport

File)– Demographic information: demo_d.xpt

• Please note that SPSS is on server and data must be saved in shared drive such as u drive or w drive. You will not be able to find the file in SPSS if you save them on your local disk.

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Task 1: Import demo_d.xpt

• Click “File”, “Open”, “Data”.

• Select the folder where demo_d.xpt is saved.

• Choose “SAS (…)” for Files of Type.

• Select demo_d.xpt.• Click “Open”.

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Task 1: Import Data

• Select the folder. • Choose agg_d file.• Select xpt format.• Click Open.

• Note: SPSS is compatible with other commonly used statistical and data management software packages. Excel, SAS, Access files are all convertible to SPSS.

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Since this is not a SPSS data file, there is no file name (untitled) in the upper left corner.

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Save demo_d f as SPSS data.

• Click “File”, “Save As”.

• File name: demo_d• Save as type:

SPSS7.0 (*sav). • Click “Save”.

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Missing Data

• In the data set, missing is in “.”, which is automatically treated missing.

• If missing data is in blank, then click “Missing”, “Discrete missing values” and enter a space.

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Task 1: Import agq_d.xpt and save it as agq_d.sav(Exercise)

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Task 2: Sort Data

• Variable to be sort: SEQN, that is, Respondent sequence number.

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Task 2: Sort agq_d.sav Data

• Select aqd_d.sav data.• Go to Data and select Sort

Cases.• On Sort Cases page, select

the variable, Respondent sequence number.

• Click on right arrow.• Choose Ascending or

Descending.• Click OK.

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Practice

• Now let’s repeat this process by doing the following:– Open the demographic data, demo_d.xpt.– Sort the data by variable, Respondent Sequence

Number.

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Sort Variables

• “Sort variable” is different from “Sort Cases”.

• This function rearranges the columns of data.

• “Sort Case” rearranges the rows of data.

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Task 3: Merge Two Data Sets

• Two data sets need to be linked by key variables.

• In our case, the key variable is SEQN-Respondent Sequence Number.

• Make sure the key variable has the same name and variable type in two data sets.

• Both data sets needs to be sorted by the key variable.

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Task 3: Merge Two Data Sets

• Under demo_d.sav data set, go to Data -> Merge File -> Add Variables

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Task 3: Merge Two Data Sets

• Choose “An open data set”.

• Click “agq_d.save” and “Continue”.

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Merge two files

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Split Files

• Very often, we like to perform separate analysis by groups (also called strata.)

• We can do so in SPSS by splitting files for groups.

• Task: In demo_d.save. Split the file by gender then get the mean of age for each gender group.

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Split File

• Under demo_d.sav, click “Data”, “Split File”.

• Choose “Organize output by groups”

• Select “Gender”• Choose “Sort the file by

grouping variables”.• Click “Ok”.

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Split Files

• Cancel the split file function when the task is done.

• Go to “Data”, “Split Files”.

• Check “Analyze all cases, do not create groups”. This is default.

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Compute Variables

• Can be used to create new variables.• Task 1: create a new variable age (month) for

the existing variable age (year)• Task 2: Log-transform age variable.

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Compute Variables

Under demo_d.xpt, go to “Transform”, “Compute Variable”.

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Log transform variables

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