215 Handout_11(chap 15)

# 215 Handout_11(chap 15) - Handout #11: Inference for...

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Handout #11: Inference for Categorical Variables STA215: Introductory Applied Statistics Dr. Jann-Huei Jinn 1. Objective : We’d like to see whether there is a relationship between two categorical variables. The hypotheses are o H : The two categorical variables are not related (independent) a H : The two categorical variables are related. Chi-square statistic 2 χ = - count expected count) expected count (observed 2 (sum is taken over r × c cells, in the following example, r × c = 3 × 2 = 6 inner cells). Degrees of freedom: df = (r - 1)(c - 1) 2. Two-Way Contingency Table : It is used to study the relationship between two categorical variables. Example : Gender Female Male Total Freshman 170( ) 100( ) 270 Class Sophomor e 50( ) 50( ) 100 Junior 60( ) 20( ) 80 Senior 20( ) 30( ) 50 Total 300 200 n=500 3. Calculating Expected Counts : The expected count for each cell in a two-way table can be calculated as

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215 Handout_11(chap 15) - Handout #11: Inference for...

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