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# Confidence interval and Student t test.

1. Dunkin Donuts advertises that a dozen of their donuts weighs about
43 oz. A certain baker has figured out that she can stay out of trouble
with her manager if each donut weighs about 3.6 oz. To test her
donut-making process, she randomly selects thirty-one donuts after
baking and weighs them. The average of the sample is 3.504 oz with s =
0.109 oz. Construct a 95% confidence interval for the true population
mean of donut weights, and then explain whether or not she will be in
trouble.

2. Scores for men (nationwide) on the verbal portion of the SAT test
are normally distributed with a mean of 509 and a standard deviation of
112. Randomly selected men are given the Columbia review course before
taking the SAT test. After the course, a sample of 49 men revealed an
average of 535 points and a standard deviation of 90 points. Using a
significance level of 0.05, test the claim that the review course
students have a mean score greater than or equal to the normal
population. (use the 5-step method).

#### Solution Summary

The solution gives step by step procedure for student t test and construction of confidence interval for mean of SAT score.

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