Warren County Telephone Company claims in its annual report that “the typical cu

Question

Warren County Telephone Company claims in its annual report that “the typical customer spends $61 per month on local and long-distance service.” A sample of 12 subscribers revealed the following amounts spent last month:

$64 $67 $63 $67 $57 $63 $69 $62 $63 $60 $54 $65

a. What is the point estimate of the population mean? (Round your answer to 3 decimal places.)

Estimated population mean $

b. Develop a 90% confidence interval for the population mean. (Use t Distribution Table.) (Round your answers to 3 decimal places.)

Confidence interval for the population mean $ and $

Explanation / Answer

a. Point estimate of the population mean is xbar=sumx/n=62.83 and sd =4.26

b. Now t value for for 90% CI with 11 df is 1.796

So margin of error is t*sd/sqrt(n)=1.796*4.26/sqrt(12)=2.209

Hence CI =mean +/-Margin of error=62.83+/-2.209=[60.62,65.04]

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