SOLUTION: Please help. I'm not understanding this questions The scores on a national test were normally distributed with a mean of 83 and a standard deviation of 8 To the nearest perce

Question 734582: Please help. I'm not understanding this questions
The scores on a national test were normally distributed with a mean of 83 and a standard deviation of 8
To the nearest percent, what percentage of test takers scored between 70 and 90
15% of test takers scored below what test score? (Round to nearest test score)
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The scores on a national test were normally distributed with a mean of 83 and a standard deviation of 8
To the nearest percent, what percentage of test takers scored between 70 and 90
z(70) = (70-83)/8 = -13/8
z(90) = (90-83)/8 = 7/8
-----
P(70< x <90) = P(-13/8 < z < 7/8) = normalcdf(-13/8,7/8) = 0.7571 = 75.71%
=========================

15% of test takers scored below what test score? (Round to nearest test score)
Draw the picture:
Find the z-score with a left tail of 15%
invNorm(0.15) = -1.0364
-----
Find the corresponding score value:
x = z*s + u
x = -1.0364*8+83 = 74.71
==============================
Cheers,
Stan H.

RELATED QUESTIONS
Hello, having some problem with this question. Can someone please help? The scores on... (answered by lynnlo)

PLEASE HELP! I HAVE TWO OTHER QUESTIONS THAT I NEED HELP WITH! IVE ATTEMPTED ALL THREE... (answered by MathLover1)

Hello, having some major issues with this question please advise. Thank you The scores (answered by Vladdroid)

Hello, having issues with this question. Please advise The scores on a national test... (answered by lynnlo)

Hello, please advise, having issues with this question. The scores on a national test... (answered by lynnlo)

Having issues with this question please advise. The scores on a national test were... (answered by stanbon)

Hello, I'm having some issues with this statistics problem. Please advise The scores... (answered by lynnlo)

This question is on normal distribution, I need some help understanding how to solve... (answered by stanbon)

Scores on an English placement test are normally distributed with a mean of 55 and... (answered by stanbon)