SOLUTION: The time taken to install a new telephone is found to be normally distributed with a mean time equal to 45 minutes and a standard deviation of 8 minutes. For a new installation,

Question 1185353: The time taken to install a new telephone is found to be normally distributed with a mean time equal to 45 minutes and a standard deviation of 8 minutes. For a new installation, what is the probability that
1. it will take more than 51 minutes
2. It will take less than 45 minutes
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
you can use the following normal distribution z-score calculator to solve this easily.

https://davidmlane.com/hyperstat/z_table.html

the first one gives you the probability it will take more than 51 minutes.

the second one gives you the probability it will take less than 45 minutes.

this calculator can be used with z-scores and with raw scores.

with z-scores, the mean is 0 and the standard deviation is 1.

with raw scores, the mean and the standard deviation are what they are as given in the problem.

when you are dealing with sample means in samples whose size is greater than 1, then you need to use the standard error, rather than the standard deviation.

this problem did not require that.

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