[riderman]

albert abbasi, vp of operations at ingleside international bank, is evaluating the service level provided to walk-in customers . Accordingly he plans a sample of waiting times for walk-in customers. If the population of waiting times has a mean of 15 minutes and a standard deviation of 4 minutes, the probability that Albert's sample of 64 will have a mean less than 14 minutes is?

[Lefko5934]

Okay so 14 minutes is 1/4 of a standard deviation from the mean. The mean essentially represents Dead center with 50% population on either side.

34.1% of the population is located between the mean and 1 standard deviation. So divi the one minute less waiting time to 1/4 of that.

Remove 8.525 from 50. That is your percent chance of having a wait time of less than 14 minutes.

41.475% is your probability or 1659 out of 40(1695/40)

I hope that makes sense.