You run a call center and you need to determine the typical length of a technical support call to your center.The research department takes a random sample of 60 calls and calculates the sample average length of a call??̅to be 15 minutes and the sample standard deviation s to be 7 minutes.a. Calculate the 99% confidence interval for µ, the population mean time for length of a technical supportcall. The z-critical value for this interval is ????2= ??0.012= ??0.005 = 2.575.b. Interpret the confidence interval in words.c. The vice president of research asserts that the mean length of a call is 10 minutes. Do you agree withthis? Explain how you know.d. Suppose your company needs a narrower confidence interval, so it can decide whether more training isnecessary for its technical support staff. Calculate the sample size necessary to estimate the population meanwithin 1 minute.
You run a call center and you need to determine the typical length of a technical support call to your center.
The research department takes a random sample of 60 calls and calculates the sample average length of a call
??̅to be 15 minutes and the sample standard deviation s to be 7 minutes.
a. Calculate the 99% confidence interval for µ, the population
call. The z-critical value for this interval is ????
2
= ??0.01
2
= ??0.005 = 2.575.
b. Interpret the confidence interval in words.
c. The vice president of research asserts that the mean length of a call is 10 minutes. Do you agree with
this? Explain how you know.
d. Suppose your company needs a narrower confidence interval, so it can decide whether more training is
necessary for its technical support staff. Calculate the sample size necessary to estimate the population mean
within 1 minute.
Step by step
Solved in 5 steps with 2 images
