# MATH

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THE MEAN PRICE OF DIGITAL CAMERAS AT AN ELECTRONIS STOR IS \$224, WITH A STANDARD DEVIATION OF \$8. RANDOM SAMPLES OF SIZE 36 ARE DRAWN FROM THIS POPULATION AND THE MEAN OF EACH SAMPLE IS DETERMINED.

• MATH - ,

First, please do not use all capitals. Online it is like SHOUTING. Not only is it rude, but it is harder to understand. Thank you.

• MATH - ,

Suppose that the population proportion of Internet users who say that they use Twitter or another service to post updates about themselves or to see updates about others is 19%. Think about selecting random samples from a population in which 19% are Twitter users.

• STAT - ,

1. In a study of the income of U.S. factory workers, a random sample of 100 workers shows a sample mean of \$35,000. Assume that the population standard deviation is \$4,500, and that the population is normally distributed.

A) Compute the 90%, 95% and 99% confidence intervals for the unknown population mean.

B) Briefly discuss what happens to the width of the interval estimate as the confidence level increases. Why does this seem reasonable?

2. In a study of the starting salary of college graduates with degrees in Accounting, a random sample of 80 graduates shows a sample mean of \$36,000 and a sample standard deviation of \$2,500. Assume that the population is normally distributed.

A) Compute and explain a 95% confidence interval estimate of the population mean starting salary for Accounting graduates.

3. A telephone poll of 950 American adults asked "where would you rather go in your spare time?" One response, by 300 adults, was "a movie". Compute and explain a 95% confidence interval estimate of the proportion of all American adults who would respond "a movie".

• MATH - ,

In a study of the starting salary of college graduates with degrees in Accounting, a random sample of 80 graduates shows a sample mean of \$36,000 and a sample standard deviation of \$2,500. Assume that the population is normally distributed.