2. A recent study of 25 students showed that they spent on average of $18.35 for gasoline per week. The standard deviation of the sample was $3.00. Construct the 90% confidence interval of the population mean.

Suppose we want a 99% confidence interval for the average amount spent on books by freshmen in their first year at college. The amount spent has a normal distribution with standard deviation $31. How large should the sample be if the margin of error is to be less than $3?

Suppose the standard deviation of the losses had been $3600 instead of $1800. What would the larger standard deviation do to the width of the confidence interval assuming the same level of confidence.

A sample mean of 62.2 was found and a 95% confidence interval of (57.3, 67.1) was also found. What is the margin of error?   a. 9.8   b. 4.9   c. 2.45   d. 3.45

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You are interested in estimating the the mean weight of the local adult population of female white-tailed deer (doe). From past data, you estimate that the standard deviation of all adult female white-tailed deer in this region to be 22 pounds. What sample size would you need to in order to estimate the mean weight of all female white-tailed deer, with a 94% confidence level, to within 6 pounds of the actual weight?

if the gpa is 2.75 of 600 students with a confidence level of 90% what is the margin of error if the standard deviation is .45

A study of 40 English professors showed that they spend, on average, 12.6 minutes correcting a student's term paper. The standard deviation was 2.5 minutes. Construct the 99% confidence interval of the mean for all term papers.

You would like to estimate the variance of sick days at a Fortune 500 company.  You randomly select 15 employees and record how many sick days they have used in the past year and you get a sample standard deviation of 1.2.  Provide a 95% confidence interval estimate of the population variance.

A newspaper article reports that the mean cost for preventative dental care per year is $175 with a standard deviation of $35 (assume that this is the population standard deviation). You want to test whether the mean cost for preventative dental care in your company is different from what was reported in the article. You take a random sample of 250 employees and find the mean cost is $171. Does this signficantly differ from what was reported in the article? Run the appropriate test at α=0.05. Give each of the following to receive full credit: 1) the appropriate null and alternative hypotheses; 2) the appropriate test; 3) the decision rule; 4) the calculation of the test statistic; and 5) your conclusion including a comparison to alpha or the critical value. You MUST show your work to receive full credit. Partial credit is available.