Algebra
posted by Jon .
The time a group of high school students arrive home from school each day was found to be normally distributed. The mean time was 3:15pm and the times had a standard deviation of 15 minutes. What is the probability that a student chosen at random arrives home from school before 2:30pm?

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Caculate Z score for this time.
Z = (x  μ)/SD
x =2:30, μ = 3:15, SD = 15
Look up the Z score in the back of your statistics text on a table of areas under the normal distribution to get your probability.
I hope this helps. Thanks for asking.