The scores on a national achievement test are normally distributed with a mean of 50 and a standard deviation of 10. Out of a group of 200 students, how many would you expect to score more than 70?
For score 70, convert to standardized value
Look up standard normal distribution table to get
or the average number of students with score of 70 or more
= P(x>70)*200=4.56 = 5 approx.
posted by MathMate