posted by StudentD .
In a psychology class of 100 students, test scores are normally distributed with a mean of 80 and a standard deviation of 5. Approximately what percentage of students have scores between 70 and 90?
You haven't memorized the proportion within 2 standard deviations from the mean?
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.
I Do not know