Suppose that you randomly survey death records for people born in 1900 in llinois and compared the life span of two different ethnicities. Of the 133 individuals sampled from ethnicity 1 , the mean life span was 42.4 years with a standard deviation of 17.8 years. Of the 90 individuals sampled from ethnicity 2, the mean life span was 36.4 years with a standard deviation of 15 years. Conduct a hypothesis test with a 5% level of significance to see if the mean life spans in Illinois were the same for the two ethnicities. Step 1: State the null and alternative hypotheses. H 0
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:μ 1
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−μ 2
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H a
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:μ 1
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−μ 2
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(So we will be performing a test.) Part 2 of 4 Step 2: Assuming the null hypothesis is true, determine the features of the distribution of the differences of sample means. The differences of sample means are with distribution mean