1. A fitness center is interested in finding a 98%

1.  

A fitness center is interested in finding a 98% confidence interval for the mean number of days per week that Americans who are members of a fitness club go to their fitness center. Records of 215 members were looked at and their mean number of visits per week was 2.5 and the standard deviation was 1.9. Round answers to 3 decimal places where possible.

a. To compute the confidence interval use a ? t z  distribution.

b. With 98% confidence the population mean number of visits per week is between  and   visits.

c. If many groups of 215 randomly selected members are studied, then a different confidence interval would be produced from each group. About  percent of these confidence intervals will contain the true population mean number of visits per week and about  percent will not contain the true population mean number of visits per week. 

2.  

You are interested in finding a 98% confidence interval for the average commute that non-residential students have to their college. The data below show the number of commute miles for 13 randomly selected non-residential college students. Round answers to 3 decimal places where possible.

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a. To compute the confidence interval use a ? t z  distribution.

b. With 98% confidence the population mean commute for non-residential college students is between  and   miles.

c. If many groups of 13 randomly selected non-residential college students are surveyed, then a different confidence interval would be produced from each group. About  percent of these confidence intervals will contain the true population mean number of commute miles and about  percent will not contain the true population mean number of  commute miles. 

3.  Isabella wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 42 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 11.6 and a standard deviation of 1.4. What is the 95% confidence interval for the number of chocolate chips per cookie for Big Chip cookies? Assume the data is from a normally distributed population. Round answers to 3 decimal places where possible.

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4.  

You must estimate the mean temperature (in degrees Fahrenheit) with the following sample temperatures:

38.324.320.745.416.926.627.727.331.319.429.3
Find the 80% confidence interval. Enter your answer as an open-interval (i.e., parentheses) accurate to 3 decimal places. Assume the data is from a normally distributed population.

80% C.I. =   

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