Sales personnel for Skillings Distributors submit weekly reports listing the cus

Question

Sales personnel for Skillings Distributors submit weekly reports listing the customer contacts made during the week. A sample of 75 weekly reports showed a sample mean of 17.5 customer contacts per week. The sample standard deviation was 5.6. Provide 90% and 95% confidence intervals for the population mean number of weekly customer contacts for the sales personnel.

90% Confidence, to 2 decimals:

( ,  )

95% Confidence, to 2 decimals:

( ,  )

Sales personnel for Skillings Distributors submit weekly reports listing the customer contacts made during the week. A sample of 75 weekly reports showed a sample mean of 17.5 customer contacts per week. The sample standard deviation was 5.6. Provide 90% and 95% confidence intervals for the population mean number of weekly customer contacts for the sales personnel.

90% Confidence, to 2 decimals:

( ,  )

95% Confidence, to 2 decimals:

( ,  )

Explanation / Answer

Mean is 16.5 and s is 5.6 , thus standard error is s/sqrt(N)=5.6/sqrt(75)=0.6466

a) For 90% confidence the z value is 1.65 thus lower limit is mean-SE*z=16.5-0.6466*1.65=15.43 and upper limit is mean+SE*z=16.5+0.6466*1.65=17.57

b) For 95% confidence, the z value is 1.96 thus lower limit is mean-SE*z=16.5-0.6466*1.96=15.23 and upper limit is mean+SE*z=16.5+0.6466*1.96=17.77

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