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STAT 301 Lab

Lab 12: Analysis of Two-Way Tables

T.A.: Yixuan Qiu

Two-Way Table

Studies the association between two categorical variables

Percentage Table

Divide each cell by the total count

Joint, Marginal, Conditional

Joint: percentage of a combination of the two factors (look for the key word "and")
Marginal: percentage of a single factor
Conditional: percentage of a single factor given that we know the value of the other factor

Example

What percentage of students have low physical activity and high fruit consumption? (Joint)

Example

What percentage of students have moderate physical activity? (Marginal)

Example

What percentage of students have low fruit consumption within the group of moderate physical activity? (Conditional)
- 17.4% / 37.4% = 46.5%

The Chi-square Test

Test whether the two factors have association

Condition to Use Chi-square Test

For tables larger than 2x2
- The average of the expected counts is 5 or more and the smallest expected count is 1 or more
For 2x2 tables
- All 4 expected cell counts are 5 or more

Enter Data in SPSS

Remember to do the WEIGHT CASES

Last Words

Thanks for your hard work in this lab
You are all GREAT!