# Question

A marketing researcher wants to find a 95% confidence interval for the mean amount that visitors to a theme park spend per person per day. She knows that the standard deviation of the amounts spent per person per day by all visitors to this park is $11. How large a sample should the researcher select so that the estimate will be within $2 of the population mean?

## Answer to relevant Questions

A company that produces detergents wants to estimate the mean amount of detergent in 64-ounce jugs at a 99% confidence level. The company knows that the standard deviation of the amounts of detergent in all such jugs is .20 ...Briefly explain the similarities and the differences between the standard normal distribution and the t distribution. For each of the following, find the area in the appropriate tail of the t distribution. a. t = 2.467 and df = 28 b. t = –1.672 and df = 58 c. t = –2.670 and n = 55 d. t = 2.819 and n = 23 Briefly explain how the width of a confidence interval decreases with an increase in the sample size. Give an example. A random sample of 36 mid-sized cars tested for fuel consumption gave a mean of 26.4 miles per gallon with a standard deviation of 2.3 miles per gallon. a. Find a 99% confidence interval for the population mean, µ. b. ...Post your question

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