STAT 207. ASSIGNMENT NO. 9

Due on Tuesday, Nov 24, 1998

Read Chapter 9

Do the following problems:

9.2

9.3

9.3' Use the data in Problem 9.3 to provide a 90% CI for the population mean, assuming that the population standard deviation is unknown and has to be estimated from the data.

9.5

9.8

9.12

9.14(Hint: Estimate the standard deviation conservatively by range/4.)

9.15

Additional Problem: A growing concern for educators in the United States is the number of teenagers who have part-time jobs while they attend high school. It is generally believed that the amount of time teenagers spend working is deducted from the amount of time devoted to school work. To investigate this problem, a school guidance counselor took a random sample of 200 15-year-old high school and asked how many hours per week each worked at a part-time job. The results were recorded and he found that the sample mean and sample standard deviation were xbar = 5.125 and s=3.310. Estimate with 95% confidence the mean amount of time all 15-year-old high school students devote per week to part-time jobs.