Question

a statistics exam had test scores with a normal distribution. the mean score was a 75 with a standard deviation of 4

Answer 1

what is the probability that a randomly selected student has a test score between 65 and 90

Answer 2

familiar of reading z-score table?

Answer 3

yes have one in front of me now

Answer 4

not sure how to use it with this question though

Answer 5

do you know how to find the z-score?

Answer 6

i know it is sample value-sample mean/ standard deviation but i dont know what to enter for the sample value

Answer 7

ok, what are the two samples values in this case?

Answer 8

65 and 90

Answer 9

do i do the average of the two

Answer 10

find the z-score for each sample value

Answer 11

-2.5 for 65 and 3.75 for 90

Answer 12

so now do i find those numbers on the z chart? for -2.5 i would have .0062 and for 3.75 i would have .9999

Answer 13

so P = P(z=3.75) - P(z=-2.5) will give you the answer

Answer 14

so .9999-.0062 gives me .9937

Answer 15

the next question asks what test score gives you the 95th percentile i would do the revese of this problem correct

Answer 16

yea

Answer 17

can u walk me through one more?