A market research company employs a large number of typists to enter data into a computer. The time it takes for new typists to learn the computer system is known to have a normal distribution with a mean of 90 minutes and a standard deviation of 18 minutes. What is the proportion of new typists who take more than two hours to learn the computer system?

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A market research company employs a large number of typists to enter data into a computer. The time it takes for new typists to learn the computer system is known to have a normal distribution with a mean of 90 minutes and a standard deviation of 18 minutes. What is the proportion of new typists who take more than two hours to learn the computer system?

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Answer 1 · 2015-02-26T12:06:53

Below is the way you do this on a TI-83 plus or similar

Go to the #Distr# menu (second-VARS) and choose NormalCdf

NormalCdf works with the following parameters:
#low# =lower boundary
#high# =upper boundary (or choose a very large number)
#mean# or average
#STD# standard deviation

So you fill in:

#"NormalCdf" (120,10^99,90,18)# and you get #~~0.0478#

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