SOLUTION: please help me solve this probability problem. 1. Given a normal distribution of values for which the mean is 75 and the standard deviation is 5. A. Find the probability that a

Question 898708: please help me solve this probability problem.
1. Given a normal distribution of values for which the mean is 75 and the standard deviation is 5.
A. Find the probability that a value between 60 and 80,inclusive.
B.Find the probability that a value is greater than or equal to 64.
C. Find the probability that a value is less than 78.
D.Find the 80th percentile for this distribution.
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
1. Given a normal distribution of values for which the mean is 75 and the standard deviation is 5.
A. Find the probability that a value between 60 and 80,inclusive.
z(60) = (60-75)/5 = -3
z(80) = (80-75)/5 = 1
----
P(60<= x <=80) = P(=3<= z <=1) = normalcdf(-3,1) = 0.0400
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B.Find the probability that a value is greater than or equal to 64.
z(64) = (64-75)/5 = -2.2
P(x >= 64) = p(z >= =2.2) = normalcdf(-2.2,100) = 0.9860
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C. Find the probability that a value is less than 78.
z(78) = (78-75)/5 = 1
P(z < 78) = P(z < 1) = normalcdf(-100,1) = 0.8413
==========================
D.Find the 80th percentile for this distribution.
invNorm(0.8) = 0.8416
----
Find the corresponding value::
x = 0.8416*5+75 = 79.21
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Cheers,
Stan H.
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