Question 1189989
z=(x-mean)/sd
so z (11 hr)=(11-13.7)/0.9 and z (12 hr)=(12-13.7)/0.9
on a calculator, use 2ndVARS 2normalcdf(11,12,13.7,0.9) for probability of 0.0281
Another way has z between -3 and -1.89 for prob. 0.00135 and 0.0294 for the same answer, subtracting the first from the second.
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85th percentile is z=1.036=(x-13.7)/0.9, and x=14.63 hours.
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this is z>(x-mean)/sigma/sqrt(n)
so z>(14-13.7)/0.9/sqrt(19)=1.453
That has probability of 0.0731