Question

Sales personnel for RH Educational Systems submit weekly reports listing the customer contacts made during the week. A sample of 65 weekly reports showed a sample mean of 19.1 customer contacts per week. The sample standard deviation was 5.4.

1. Determine a 90% confidence interval for the population mean number of weekly customer contacts for the sales personnel. Round the endpoints of the interval to 2 decimal places.

2. Determine a 95% confidence interval for the population mean number of weekly customer contacts for the sales personnel. Round the endpoints of the interval to 2 decimal places.

Answer 1

it is given that the sample size is n = 65, mean = 19.1 and standard deviation is s = 5.4

sample size is large enough, i.e. more than 30, so we will assume that the sample standard deviation is equal to the population standard deviation

(A) z score for 90% confidence interval is z = 1.645 (using the z distribution table)

confidence interval =

this implies

(B)

z score for 95% confidence interval is z = 1.96 (using the z distribution table)

confidence interval =

this implies