The time spent waiting in the line is approximately normally distributed. The mean waiting time is 4
minutes and the variance of the waiting time is 1. Find the probability that a person will wait
for more than 5 minutes. Round your answer to four decimal places.
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This probability is the area under the specified normal curve on the right of the z-score z= 5 minutes.
To find the value, use the standard function normalcdf on your regular calculator TI-83/84.
The format is
P = normalcdf(z1, z2, mean, SD)
In this problem, take z1 = 5 minute, z2 = 9999 (as infinity); mean = 4 minutes (given); SD = 1 = .
You will get P = normalcdf(5, 9999, 4, 1) = 0.1587 (rounded).
Solved.
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Alternatively, you can use free of charge online calculator at this web-page
https://davidmlane.com/hyperstat/z_table.html
Use it in the mode "Area from a value".