SOLUTION: The midterm exam scores in a large stat class in a certain university is normally distributed with a mean score of 60 and a standard deviation of 12. a. Find the probability tha

Question 927344: The midterm exam scores in a large stat class in a certain university is normally distributed with a mean score of 60 and a standard deviation of 12.
a. Find the probability that the student will get a score greater than 65?
b. Find the probability that the student will get a score less than 57?
c. If there are 200 students. How many of them got a grade of less than 55?
d. If the highest 70% of the class passed, what is the lowest passing score?
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!
mean score of 60 and a standard deviation of 12.
.........
P(x > 65) = P(z > 5/12) = normalcdf(.4167,100) = .3384 0r 33.84%
......
P(x < 57) = P(z < -3/12)= normalcdf(-100, -.25) = .4013 0r 40.13%
.........
P(x < 55) = P(z < -5/12) = normalcdf(-100, -.4167)= .3384
200(.384)= 67.68, 68 got a grade of less than 55
............
12invNorm(.30) + 60 = X
X = 12(-.5244) + 60 = 53.7. 54 is the lowest passing score

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