SOLUTION: AM VERY CONFUSED...PLEASE HELP X has a normal distribution with a mean of 80.0 and a standard deviation of 4.0. Find the following probabilities: SHOW ALL WORK (A) P(x

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Question 489203: AM VERY CONFUSED...PLEASE HELP
X has a normal distribution with a mean of 80.0 and a standard deviation of 4.0. Find the following probabilities: SHOW ALL WORK
(A) P(x < 79.0)
(B) P(78.0 < x < 83.0)
(C) P(x > 86.0) (Points : 6)

Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
X has a normal distribution with a mean of 80.0 and a standard deviation of 4.0. Find the following probabilities: SHOW ALL WORK
(A) P(x < 79.0)
z(79) = (79-80)/4 = -1/4
P(x < 79) = P(z < -1/4) = normalcdf(-100,-1/4) = 0.4013
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(B) P(78.0 < x < 83.0)
z(78) = (78-80)/4 = -1/2
z(83) = (83-80)/4 = 3/4
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P(78.0 < x < 83.0) = P(-1/2 < z < 3/4) = 0.4648
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(C) P(x > 86.0)
z(86) = (86-80)/4 = 6/4 = 3/2
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P(x > 86.0) = P(z > 3/2) = 0.2266
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Cheers,
Stan H.

SOLUTION: AM VERY CONFUSED...PLEASE HELP X has a normal distribution with a mean of 80.0 and a standard deviation of 4.0. Find the following probabilities: SHOW ALL WORK (A) P(x < 79.