Hi all can somebody help me with this: An educational testing corporation has de

Question

Hi all can somebody help me with this:
An educational testing corporation has designed a standard test ofmechanical aptitude. Scores on this test are normally distributedwith a mean of 75 and a standard deviation of 15.

a) If a subject is randomly selected andtested, find the probability that his score will be below 85.
b) If a subject is randomly selected and tested, find theprobability that his score will be greater than 80.
c) If a subject is randomly selected and tested, find theprobability that his score will be between 60 and70.

Please show all work, Thank You will give aLifesaver.

Explanation / Answer

z = (actual score - mean) / standard deviation mean = 75 standard deviation = 15 z = (X - 75) / 15 a) z(85) = (85-75)/15 = .667 Using a z table, we find that the area below this z value is.7486. Thus there is a 74.86% chance he will score below thisvalue. b) z(80) = (80 - 75) / 15 = .333 Again using a z table, we find that the area below this z value is.6293. Thus, the probability of scoring above this is 1 -.6293 = .3707. c) z(60) = (60 - 75) / 15 = -1 Using a z table, we find that the area below this z value is.1587. z(70) = (70 - 75) / 15 = -.333 Using a z table, we find that the area below this z value is.3707. Taking the difference, we find that the probability of scoringbetween these two scores is .3707 - .1587 = .212. You have asked a few questions like this in the past few minutes,is there anything in specific I can help you with that you are notcurrently understanding fully?

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