1. A sample of the prices for a particular pair of Nike shoes was collected from 16 randomly selected stores. Prices of these Nike shoes are normally distributed. The following prices were noted:
95, 108, 97, 112, 99, 106, 105, 100, 99, 98, 104, 110, 107, 131, 121, 120.
Find a 90% confidence interval for the mean price of the pair of Nike shoes.
State the parameter
State the random variable
State and check the assumptions.
Calculate the confidence interval and state it in interval form. Round to the nearest tenth (one decimal place).
State the conclusion.
2. Suppose that a market research firm is hired to estimate the proportion of adults living in a large city who have cell phones. Five hundred randomly selected adult residents in this city are surveyed to determine whether they have cell phones. Of the 500 people sampled, 422 responded yes – they own cell phones. Find a 99% confidence interval for the proportion of adult residents of this city who have cell phones.
State the parameter
State the random variable
State and check the assumptions.
Calculate the confidence interval and state it in interval form. Round to the nearest hundredth (two decimal places).
State the conclusion.
3. As the confidence level decreases, the confidence interval gets narrower. Circle the correct answer.
True False
4. The confidence interval is made up of a point estimate plus and minus the margin of error. Circle the correct answer.
True False
5. The point estimate in a confidence interval is the sample statistic. Circle the correct answer.
True False
6. The purpose of a confidence interval is to estimate a statistic. Circle the correct answer.
True False
