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Unformatted text preview: STA 3024: Homework 3 Solution Data: Cocaine/Heroin Marijuana Yes No Total Yes 8 54 62 No 10 94 104 Total 18 148 166 1. For our sample data, calculate the conditional distribution of whether or not students have used cocaine/heroin, given whether or not they have used marijuana. (Your answer should be a 2 × 2 table of conditional percentages.) Cocaine/Heroin Marijuana Yes No Total Yes 8/62=12.9% 54/62=87.1% 100% No 10/104=9.62% 94/104=90.38% 100% 2. Now let’s use this data to conduct a chi-squared test with α = 0 . 05. (a) Calculate each cell’s expected count for the chi-squared test. (Your answer should be a 2 × 2 table of expected counts.) Cocaine/Heroin Marijuana Yes No Yes 62*18/166=6.72 62*148/166=55.28 No 104*18/166=11.28 104*148/166=92.72 (b) State the assumptions made by the chi-squared test. For each assumption, state whether or not it is satisfied by our data. • Two categorical variables • Simple random sample from the population of interest • Expected (observed) count in each cell should be at least 5.Expected (observed) count in each cell should be at least 5....
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This note was uploaded on 12/15/2011 for the course STA 3024 taught by Professor Ta during the Spring '08 term at University of Florida.
- Spring '08