SOLUTION: A group of more than 1000 students took a test in Mathematics and their final grades have a mean of 70 and a standard deviation of 10. If we can approximate the distribution of the

Question 1149161: A group of more than 1000 students took a test in Mathematics and their final grades have a mean of 70 and a standard deviation of 10. If we can approximate the distribution of these grades by a normal distribution, what percent of the students
(a) scored higher than 80?
(b) should pass the test (grades ≥ 60)?
Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
(a) Probability (P) (X > 80) = 1 - P(X < 80)
:
z-score(80) = (80 - 70)/10 = 1
:
Lookup a z-score of 1 in the table of z-values and its associated P
:
P(X < 80) = 0.8413
:
P(X > 80) = 1 - 0.8413 = 0.1587
:
(b) z-score(60) = (60 -70)/10 = -1
:
P(X < 60) = 0.1587
:
P(X > 60) = 1 - 0.1587 = 0.8413
:

RELATED QUESTIONS
A large group of students took a test in physics and the final grade have a mean of 70... (answered by Boreal)

A Large group of students took a test in Math and the final grades have a mean of 75 and... (answered by Boreal)

A large group of students took a test in Physics and the final grades have a mean of 80... (answered by Theo)

On national mathematics tests, the mean is 75, with a standard deviation of 10. The... (answered by stanbon)

Is 120.5 correct? A standardized test has a mean of 600 and a standard deviation of 75.... (answered by stanbon)

A standardized test has a mean of 600 and a standard deviation of 75. If 1000 students... (answered by stanbon)

Please, please and thx in adv. I have been studying for almost 4 days already for my... (answered by stanbon)

The mean and standard deviation of 500 students who took a statistics final were 72 and... (answered by Boreal)

The mean and standard deviation of 500 students who took a statistics final were 72 and... (answered by stanbon)