After years of data collection by college students, it has been determined that the distribution of course grades in Ms. Green’s Statistic II class follows a normal distribution with a mean of 62 and a standard deviation of 14.
(a) A student will pass Ms. Green’s course if he or she receives a course grade of 70 or higher. A current student in Ms Green’s class is chosen at random. What is the probability that the student will NOT receive a passing grade in Ms. Green’s class?
(b) What is the probability of a student receiving a “B” (i.e. a course grade greater than or equal to 80, but less than 90) in Ms. Green’s class?
(c) What range of course grade values would be considered outliers for Ms. Green’s class?
statistics - PsyDAG, Monday, May 9, 2011 at 11:44am
a. Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to that Z score.
b. Use same equation to find proportions between the two Z scores.
c. I would say any score > ± 3 SD.
I'll let you do the calculations.