Question

You may need to use the appropriate appendix table or technology to answer this 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 Need Help? Read it Watch Masterit Talk to a Tutor

Answer 1

a) For n - 1 = 66 degrees of freedom, we get from the t distribution tables that:
P( -1.668 < t₆₆ < 1.668) = 0.9

Therefore the 90% confidence interval here is obtained as:

X +

19.5 +1.668 * V67

19.5±1.05965

(18.44. 20.56)

This is the required 90% confidence interval here.

b) From t distribution tables, we have here:
P( -1.997 < t₆₆ < 1.997) = 0.95

Therefore the confidence interval here is obtained as:

X +

19.5 +1.997* 67

19.5±1.2687

(18.23, 20.77)

This is the required 95% confidence interval here.