Question

The mean score was a 75 with a standard deviation of four.....

Answer 1

Can someone walk me through how to solve this
1) A statistics exam has test scores with a normal distribution. The mean score was a 75 with a standard deviation of four.

-what test score gives the 95th percentile?

Answer 2

You can standardize first.
\[\frac{X-75}{4}=Z\]

You can find the 95th percentile looking at a standard normal distribution table. Then you can use the above relation to see how you can get the given test score.

Answer 3

okay! thanks so heres what i have. .9495 is 1.64 and .9505 is 1.65, so as far as i remember I average the 2? SO 1.645.

1.645 = x-75/4
x=81.58

Answer 4

Yes

Answer 5

Can you check this one for me?
(within the same question)
what is the probability that a randomly selected student has a test score between 65 and 90

z score = -2.5 for 65 and 3.75 for 90
so P = P(z=3.75) - P(z=-2.5)
so .9999-.0062 gives me .9937

Answer 6

Thank you sooo much, you are my statistics savior! Hahaha

Answer 7

Yes looks good to me :)

Answer 8

Haha I love stats