Statistic in Social Science
posted by Rhea .
The verbal part of the Graduate Record Exam (GRE) has a mean of 500 and a standard deviation of 100. Use the normal distribution to answer the following questions:
a. If you wanted to select only student at or above the 90th percentile, what verbal GRE score would you use as a cutoff score?
b. What verbal GRE score corresponds to a percentile rank of 15%? What verbal GRE score corresponds to a percentile rank of 55%?
c. What's the percentile rank of a GRE score of 628? What's the percentile rank of a GRE score of 350?
d. If you randomly selected 1,500 students who had taken the verbal GRE, how many would you expect to score lower than 250? How many would you expect to score higher than 750?

Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability(.90, .15, etc.) and related Z score. Insert into above equation and solve for score.
For last two (c & d) solve for Z and use the same table. 
4. The verbal part of the Graduate Record Exam (GRE) has a ƒÝ of 500 and ƒã = 100. Use the normal distribution to answer the following questions:
a. If you wanted to select only students at or above the 90th percentile, what verbal GRE score would you use as a cutoff score?
b. What verbal GRE score corresponds to a percentile rank of 15%? What verbal GRE score corresponds to a percentile rank of 55%?
c. What¡¦s the percentile rank of a GRE score of 628? What¡¦s the percentile rank of a GRE score of 350?
d. If you randomly selected 1,500 students who had taken the verbal GRE, how many would you expect to score lower than 250? How many would you expect to score higher than 750?