STAT Questions

STAT 415: Assessment #2 Quiz

You must show all of your work in order to receive full and/or partial credit.

1. (8 points) Advertisements for the Sylph Physical Fitness Center claim that completion of their course will result in a loss of weight (measured in pounds). A random sample of 8 recent students revealed the following body weights before and after completion of SPF course.

Student 1 2 3 4 5 6 7 8

Before 155 228 141 162 211 185 164 172

After 154 207 147 157 196 180 150 165

The above data summarizes to the following (Note that “Difference = Before - After”).

Mean Std Dev

Before 177.25 29.325

After 169.50 22.431

Difference 7.75 8.598

Construct a 95% confidence interval for the mean weight loss for the population represented by this sample assuming that the differences are coming from a normally distributed population.

2. (12 points) Two preservatives, tested and determined safe for use in red meats, are to be compared for their effects on retarding spoilage. Fifteen cuts of fresh red meat are treated with preservative A and another fifteen cuts of fresh red meat are treated with preservative B. The cuts are placed in a chilled container and the number of hours until spoilage begins is recorded for each. The results are summarized in the table below.

Preservative Sample Size Sample mean Sample sd

A 15 257.3 12.8

B 15 249.8 9.7

Estimate the difference between the true mean times until spoilage for the two preservatives using a 98% confidence interval. Write a sentence interpreting the confidence interval.