Question

Sales personnel for Skillings Distributors submit weekly reportslisting the customer contacts made during the week. A sample of 65weekly reports showed a sample mean of 19.5 customer contacts perweek. The sample standard deviation was 5.2. Provide 90% and 95%confidence intervals for the population mean number of weeklycustomer contacts for the sales personnel.

90% Confidence, to 2 decimals:

( . )

95% Confidence, to 2 decimals:

( , )

Answer 1

ANSWER:

Given information is Salespersonnel for Skillings Distributors submit weekly reports listingthe customer contacts made during the week. A sample of 65(n)weekly reports showed a sample mean of 19.5(x-bar) customercontacts per week. The sample standard deviation was5.2(s).

The formula forcalculating 90% confidence intervals for the population meannumber of weekly customer contacts for the sales personnel is givenby

here t_α/2,n-1 =t_0.1/2,65-1 = 1.66
Substitute the values we have

Similarly for 95% we have

here t_α/2,n-1 =t_0.05/2,65-1 =1.99         [t-table valueat 95% CI]

Substitute the values wehave

(OR) TRY THIS SIMPLY WAY

Confidence Interval -

90% CI - (18.44,20.56)

95% CI - (18.23,20.76).

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