Chi-Square with SPSS
The Chi Square (X2) test of independence is designed to examine whether two categorical variables are related to each other in a way not expected by chance. For instance, suppose I wanted to see if males and females differed in terms of whether they prefer vanilla or chocolate ice cream. Assume that for gender, 1 = female, 2 = male and for icecream, 1 = vanilla and 2 = chocolate.
Here is the sample data set:
To compute the X2 test for independence, follow the following steps
1. click on ‘analyze’
2. click on ‘descriptive statistics’
3. click on ‘crosstabs’
4. click on ‘statistics’
5. choose ‘chi-square’ and click ‘continue’
6. choose one of your categorical variables for ‘row’ and the other for ‘column’
7. click ‘paste’
8. highlight the commands
9. click on ‘run’
10. click on ‘selection’
Your output will look about like so:
Here you are concerned with the Pearson Chi Square. In this case, the X2(1) is 1.67, ns. You would write it up accordingly – perhaps as follows:
This analysis was conducted to examine if males and females differ significantly in their preference for vanilla as opposed to chocolate ice cream. The X2 test for independence suggested that there is no significant relationship between gender and ice cream choice (X2(1) = 1.67, ns).
X2 on data collected in class.
Get into groups of 3 or 4. Think of a hypothesis that would include two categorical variables.
A. Create a .sav file
B. Create two nominal variables – with at least 2 values each
C. Make them variables that can actually be collected – either from other students in class or variables that can somehow be collected on the Web
D. Conduct a X2 test for independence.
E. Write up a brief report summarizing (a) the hypothesis being addressed, (b) the nature of the data being examined, (c) the analysis being conducted, (d) the results (including text in the Results section and a table), and (e) implications of the results.
F. Give brief report to class that presents data from table and Chi Square results