Why are you substituting 5 for =?
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability (.025 because it is two-tailed) and its Z score. Insert Z first as positive and later as negative into above equation.
Calculate and come to your own conclusions.
In the population of typical college students, _ 5 75 on a statistics final exam _X 5 6.42 . For 25 students who studied statistics using a new technique, X 5 72.1. Using two tails of the sampling distribution and the .05 criterion: (a) What is the critical value? (b) Is this sample in the region of rejection? How do you know? (c) Should we conclude that the sample represents the population of typical students? (d) Why?
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