lectures (topic-2, lec-4)

8/7/2019 Lectures (Topic-2, Lec-4)

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Training Course on SPSS for Professionals, Researchers an

Students

Lecture 04: Data Manipulation II

Data Manipulation II includes:

A. Splitting File

B. Case Selection

C. Selecting a Random Sample

D. Weight Cases

To learn the above manipulation techniques, let us enter the following data into SPSS and save it in

computer.

Subject Sex Age Religion EducationIncome per

day

1 1 25 1 15 100

2 1 32 2 15 200

3 1 30 3 16 150

4 2 24 1 13 125

5 2 20 2 12 1206 2 27 3 19 125

7 1 25 1 12 175

8 1 33 2 13 200

9 2 39 3 15 120

10 2 40 1 17 125

11 1 32 2 11 135

12 2 27 3 10 130

13 1 37 3 14 100

14 1 19 2 12 150

15 2 25 1 15 120

Sex : 1 = Male, 2 = Female

Religion : 1 = Muslim, 2 = Hindu, 3 = Christian

A. Splitting File

You may encounter some situations where you need to analyze data based on the categories of one

or more categorical variables. For example, you might seek to know the picture of income or

education among the sexes either for comparison purposes or for organizing the output by groups.

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Students

To do this you have the SPSS tool Split File.

Split File splits the data file into separate groups for analysis based on the values of one or more

grouping variables. If you select multiple grouping variables, cases are grouped by each variable

within categories of the prior variable on the Groups based on list. For example, if you select Sex as

the first grouping variable and Religion as the second grouping variable, cases will be grouped by

Religion classification within each Sex category.

Note that you can specify up to eight grouping variables and cases should be sorted by values of the

grouping variables.

1st Approach: Group Comparison

Suppose you want to compare income of the sexes. Then it would be convenient if the results are

shown in a single table for both sexes separately. So to get output in that format you should do

splitting the data file. And you can split your data file just following the instructions given below:

Click on Data (Menu Bar) and then Split File

Select Compare Groups

Now select the variable Sex and send it to the box Groups Based on:

ClickOK

Now if you carry out any analysis on this data file you will get the results in your desired format.

Again you may seek to compare income among people of different religions and sexes at a time.

Repeat the above steps. Here with Sex variable select the variable Religion and send it to the box

Groups Based on, click OK.

2nd Approach: Organizing Output by Groups

Suppose you want the results are displayed separately in different table for each split-file group.

For example, you might desire to summarize the information on education variable for people of

varied religions separately in different tables. To do this, follow the instructions given below:

Click on Data (Menu Bar) and then Split File

Select Organize output by groups

Now select the variable Religion and send it to the box Groups Based on:

ClickOK.



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Students

Similarly try for other variables (say Sex).

You can use the Toolbar item to Split a data file. Just click on the Split File tool. And the Split File

box will appear. Now you can do all the steps as before.

B. Case Selection

Sometimes you may have special interest on particular cases only. To cope with this situation,

SPSS will have for you the Select Cases option. For instance, suppose you want to analyze data

considering only male respondents/cases. Then you have to select only male cases. To do it, use the

following instructions:

Click on Data (Menu Bar)

Select Cases

Select If Condition is Satisfied

Click on If

Select the variable sex and send it to the expression box.

Click on = sign on the calculator pad, click on 1 and then Continue

Select Unselected Cases are Filtered

Click on OK.

Again suppose you want to study only Hindu and Christian people. Then select these cases

following the instruction given below:

Click on Data, Select Cases, Select If condition is satisfied

Click on If, send the variable Religion to the expression box

Click on sign and 2 in the calculator pad

Click on OK.

Again you might want to study only Muslim females. You can select the desired cases simply by

taking Sex and Religion variables in the expression box of Select cases: If and writing them as

follows:

sex = 2 & religion = 1

Now click on Continue and then OK.



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Students

C. Selecting a Random Sample

You can also take random sample of cases. The sample size may be an approximate percentage of

all cases or you can exactly mention the sample size. Suppose you will select a random sample of

size 40% of all cases in your data file. To do this, follow the instructions below:


Select Random Sample of Cases

Click on Sample

Select Approximately and write 40% in the boxClick on Continue and then OK.

Again suppose you will select a random sample of size 7 from all cases in your data file. To do this,

follow the instructions below:


Select Random sample of Cases

Click on Sample

Select Exactly and write 7 in the 1st box and 15 in the 2nd box

Click on Continue and then OK.

You can also take a sample just mentioning the range of cases. For example, you may need to study

some consecutive cases from anywhere of the data file (say, cases from 5 to 12). To do this, follow

the instructions given below:


Select Based on time or case range

Click on Range, write 5 in the First Case box and write 12 in the Last Case box

Click on Continue and then OK.

D. Weight Cases

Weight Cases gives cases different weights for statistical analysis. The values of the weighting

variable should indicate the number of observations represented by single cases in your data file.

Note that Cases with zero, negative, or missing values for the weighting variable are excluded from



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