statistics
posted by carly .
if a test has a mean of 150 and a standard deviation of 30, we know that:
a)50% of the respondents scored between 180 and 210
b)68% of the responents scored above 120
c)50% of the respondents scored between 120 and 210
d) 96% of the respondents scored between 90 and 210

Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the various Z scores.