SOLUTION: The time required to finish a test in normally distributed with a mean of 40 minutes and a standard deviation of 8 minutes. What is the probability that a student chosen at random

Question 828845: The time required to finish a test in normally distributed with a mean of 40 minutes and a standard deviation of 8 minutes. What is the probability that a student chosen at random will finish the test in less than 48 minutes?
Please help !!
A. 84%
B. 2%
C. 34%
D. 16%

Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!

If the student finished at the mean, that means 50% of the students finished in less than 40 minutes and 50% of the students finished greater than 40 minutes.
Finishing in 48 minutes is the mean plus one standard deviation so the probability is greater than 50%.
From the answers above, only one answer works.
Usually it's not that simple.
Looking at a normal distribution curve at 1 standard deviation greater than the mean, the cumulative probability is 0.841 or 84.1%.
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