A sample of 160 calls to a customer help line during the week found callers there were kept waiting on average for 22 minutes with s = 7. (a) Find the margin for error for this survey if we use a 95% confidence interval for the length of time all customers during this period are kept waiting. (b) Interpret for management the margin of error. (c) If we only need to be 90% confident, does the confidence interval become wider or narrower? (d) Find the 90% confidence interval.
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93% in this case), standard deviation is the population standard deviation (which we don't know, so we'll use the sample standard deviation as an estimate), and sample size is 160. We can estimate the population standard deviation using the sample standard Show more…
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A sample of 180 calls to a customer help line during the week found callers there were kept waiting on average for 22 minutes with s=7. (a) Find the margin for error for this survey if we use a 95% confidence interval for the length of time all customers during this period are kept waiting. (b) Interpret for management the margin of error. (c) If we only need to be 90% confident, does the confidence interval become wider or narrower? (d) Find the 90% confidence interval.
Penny R.
On a particular day a consumer-advice bureau received 125 calls. For a random sample of 40 of these calls, it was found that mean time taken in providing the requested advice was $7.28$ minutes, and the sample standard deviation was $5.32$ minutes. a. Find a $99 \%$ confidence interval for the mean time taken per call. b. Find a $90 \%$ confidence interval for the total amount of time taken in answering these 125 calls.
Determine the margin of error for a confidence interval to estimate the population mean with n = 18 and s = 14.5 for the confidence levels below. a) 80% b) 90% c) 99% a) The margin of error for an 80% confidence interval is . (Round to two decimal places as needed.) b) The margin of error for a 90% confidence interval is . (Round to two decimal places as needed.) c) The margin of error for a 99% confidence interval is . (Round to two decimal places as needed.)
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