Question

The scores on a chemistry exam were normally distributed with a mean of 65 and a standard deviation of 9.
a. what percent of the students scored above 65?
b. what percent of the students scored above 56?
c. what percent of the students scored below 47?
d. what percent of the students scored between 65 and 74?
e. what percent of the students scored between 56 and 83?
f. If 1,000 students took the exam and all students with grades 74 and 83 earned a B, how many students earned a B?
g. how high must a student score in order to be in the top 2.5% of scores?

Answer 1

you use the same table as the previous post.

Z for the first score 65 = 65-65 / 9 = 0

Answer 2

what is the reading for 0?

Answer 3

http://math.arizona.edu/~rsims/ma464/standardnormaltable.pdf

Answer 4

.50000

Answer 5

right so that simply means that 1 - 0.5 = 0.5 = 50% is the answer

Answer 6

Z score for b is 56-65 / 9 = -1

Answer 7

so I look for the -1 reading?

Answer 8

yea

Answer 9

my reading shows .15866

Answer 10

right
remember this represents the area to the left of the Z score. But we require the area to the RIGHT becuase we have scores of above 56

Answer 11

NOw the area of the whole graph is 1 so the answer is
1 - 0.15866


do you understand that ?

Answer 12

yes I do understand I was thinking of it myself

Answer 13

good

Answer 14

c is a direct reading because our table gives values below the Z score .
so for scores < 47 the Z score is 47-65 / 9 = -2

just read -2 off the table.

Answer 15

sorry gtg right now