How do you construct a 95% confidence interval?
You work for a consumer advocate agency and want to find the mean repair cost of a washing machine. As part of your study, you randomly select 40 repair costs and find the mean to be $100. The sample standard deviation if $17.50. How do you construct a 95% confidence interval for the population mean repair cost?
You work for a consumer advocate agency and want to find the mean repair cost of a washing machine. As part of your study, you randomly select 40 repair costs and find the mean to be $100. The sample standard deviation if $17.50. How do you construct a 95% confidence interval for the population mean repair cost?
1 Answer
Apr 23, 2018
Explanation:
Given the mean, standard deviation, the number of samples and the desired confidence interval, the interval is calculated from the following formula:
where z is from the standard distribution tables (in the reference), and is 1.96 for a CI of 95%.