Question

Sales personnel for Skillings Distributors submit weekly reports listing the customer contacts made during the week. A sample of 67 weekly reports showed a sample mean of 19.5 customer contacts per week. The sample standard deviation was 5.2.

Provide a 90% confidence interval for the population mean number of weekly customer contacts for the sales personnel. (Round your answers to two decimal places.)

contacts/week to contacts/week

Provide 95% confidence interval for the population mean number of weekly customer contacts for the sales personnel. (Round your answers to two decimal places.)

contacts/week to contacts/week

Answer 1

Solution :

(a)

t _/2,df = 1.668

Margin of error = E = t_/2,df * (s /n)

= 1.668 * (5.2 / 67)

Margin of error = E = 1.06

The 90% confidence interval estimate of the population mean is,

- E < < + E

19.5 - 1.06 < < 19.5 + 1.06

18.44 < < 20.56

(18.44 , 20.56)

(b)

t _/2,df = 1.997

Margin of error = E = t_/2,df * (s /n)

= 1.997 * (5.2 / 67)

Margin of error = E = 1.27

The 95% confidence interval estimate of the population mean is,

- E < < + E

19.5 - 1.27 < < 19.5 + 1.27

18.23 < < 20.77

(18.23 , 20.77)