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Hello professor, for homework 9.10 numbers 42 and 45 aren't fractions. How do I know which d.f to look up in the top row and which to look up in the left column. Both problems have the same exact claim yet in number 42, n2 is on the top row and n1 is on the left column...but number 45 is the opposite, n1 is on the top and n2 is on the left. I don't understand this because the claims for both problems are identical. Thanks.

Posted to STATS 2 on Wednesday, October 8, 2014   Replies: 1

Professor Mcguckian
10/09/2014
1:25 AM EST

Hi Cristina,

It is not the claim that determines the test statistic in these problems. We use the sample variances to determine the test statistic, which in turn, leads to the critical value. The test statistic is formed by placing the larger standard deviation or variance on top of the fraction. The sample that has the larger standard deviation (or variance) becomes your numerator, and the sample size associated with that sample is what leads to the numerator degrees of freedom.