Chi-Square Test

 

A chi-square test (also called Pearson’s chi-squared test) is used to assess two types of comparison: tests of goodness of fit and tests of independence (here)

The test of independence is applied when you have two categorical variables from a single population. It is used to determine whether there is a significant association between the two variables.

Suppose that Variable A has r levels, and Variable B has c levels. The null hypothesis states that knowing the level of Variable A does not help you predict the level of Variable B. That is, the variables are independent.

H0: Variable A and Variable B are independent.
Ha: Variable A and Variable B are not independent.

The alternative hypothesis is that knowing the level of Variable A can help you predict the level of Variable B (not independent).

Expected cell count rule: Adequate expected cell counts needed. A common rule is 5 or more in all cells of a 2-by-2 table, and 5 or more in 80% of cells in larger tables, but no cells with zero expected count. When the expected cell counts less than 5, using Fisher’s exact test instead.

 

How to do this test in SAS ?

How to do it in R ?

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