in order to fairly set flat rates for auto mechanics, a shop foreman needs to estimate the average time it takes to replace a fu
el pump in a car. how large a sample must he select if he wants to be 99% confident that the true average time is within 15 minutes of the sample average? assume the standard deviation of all times is 30 minutes.
The value of n is 25 according to standard deviation in the question.
What is standard deviation?
Standard Deviation is a measure that shows what quantity variation (such as unfold, dispersion, spread,) from the mean exists. the quality deviation indicates a “typical” deviation from the mean. it's a well-liked live of variability as a result of it returns to the first units of live of the info set.
Main body:
s = 30 minutes
C.I. = 99%
mean = 15 minutes
z value for 99% = 2.58
mean = z*s/√n
15 = 2.58 * 30 / √n
√n = 5.06
n = 25
Hence the value of n is 25 .
To know more about standard deviation click on the link below
