How many degrees of freedom should they use in their calculations? df=
Suppose that Rachel studied for the Graduate Management Admission Test (GMAT) using a well-known preparation class and was thrilled to receive a total score of 760. Her friend Eric, however, thinks she would have scored just as well without the class.
To test the efficacy of the class, they obtain a small but random sample of 15 test results from other students using the same class. This sample's average is 567.23 with a standard deviation of 182.05. In comparison, the national average was 550.12. Assume the population's results are
Rachel and Eric decide to perform a two-tailed ?‑test at a significance level of ?=0.05. How many degrees of freedom should they use in their calculations?
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