The verbal part of the graduate record exam has a mean (?) of 500 and a standard deviation (?) of 100. Use the normal distribution to answer the following questions:
a. if we wanted to select only students at or above the 90th percentile, what verbal GRE score would we use as a cutoff?
b. what verbal GRE score corresponds to a percentile rank of 15%? 55%?
c. what is the percentile rank of a verbal GRE score of 628? 350?
d. if we randomly selected 1500 students who had taken the verbal GRE, how many would we expect to score lower than 250? higher than 750?