Posted by Tracy on .
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?
what formula would i use to solve for this?

Algebra 
PsyDAG,
Z score = (xμ)/SD, where x is the individual score, μ = mean, and SD = standard deviation.
Once the Z score is obtained, look it up in a table in the back of your statistics text called something like "areas under the normal distribution" to get the probability.
I hope this helps. Thanks for asking.