Question 974386: Suppose that historically the final exam scores for Bus 101 follow the Normal
distribution with mean 70 and standard deviation 15. Use a Z table (not software)
to get your answers.
What proportion of students is expected to get 80 or greater on the exam?
b) What proportion of students is expected to get 45 or less on the exam?
c) What proportion of students is expected to get between 52 and 90 on
exam?
d) If the grading policy is to give an “A” to the top 15% of the scores, what is
the cutoff for an “A”?
e) If the grading policy is to give an “F” to the bottom 7% of the scores,
getting what score or less gives an “F”?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! mean=70
sd=15
>80 is >z=0.67 ;;0.253
45 or less is -1.67 sds or 0.0475
between 52 and 90 is sd -1.2 to sd 1.33 or about 0.794
It is about 1.04 sd or 15-16 points above the mean. That would be an 85,86.
It is about -1.475 SDs or about 22 points below the mean, or a 48.
These may be off slightly due to interpolation, but the idea is (score-mean)/sd = z -score
|
|
|
