SOLUTION: A professor gives an exam to one of their classes. Suppose the test scores were normally distributed, with a mean of 72 and a standard deviation of 11. a) What percentage of scor

Algebra ->  Probability-and-statistics -> SOLUTION: A professor gives an exam to one of their classes. Suppose the test scores were normally distributed, with a mean of 72 and a standard deviation of 11. a) What percentage of scor      Log On


   

Question 464253: A professor gives an exam to one of their classes. Suppose the test scores were normally distributed, with a mean of 72 and a standard deviation of 11.
a) What percentage of scores will fall below 50?
b) The students who scored in the bottom ten percent must take the exam again. What score must a student score below to be in this group?

Answer by reviewermath(1029) About Me  (Show Source):
You can put this solution on YOUR website!
a. z=%2850-72%29%2F11=-2
P%28Z%3C-2%29+=+0.02275
b. P%28Z%3C-1.282%29+=+0.10
therefore %28X-72%29%2F11=-1.282
X=57.90
The score a student must score below to be in this group is 57.90.