SOLUTION: Hi! Please help me with this. The scores of students in the NAT is normally distributed with a mean of 60 and a standard deviation of 8. If 50 students took the test, how many g

Algebra ->  Probability-and-statistics -> SOLUTION: Hi! Please help me with this. The scores of students in the NAT is normally distributed with a mean of 60 and a standard deviation of 8. If 50 students took the test, how many g      Log On


   

Question 853814: Hi! Please help me with this.
The scores of students in the NAT is normally distributed with a mean of 60 and a standard deviation of 8. If 50 students took the test, how many got scores above 36?
Will really appreciate any kind of help!
Found 2 solutions by stanbon, ewatrrr:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
The scores of students in the NAT is normally distributed with a mean of 60 and a standard deviation of 8. If 50 students took the test, how many got scores above 36?
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z(36) = (36-60)/8 = -24/8 = -3
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P(x > 36) = P(z > -3) = normalcdf(-3,100) = 0.9987
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# who scored above 36 = 0.9987*50 = 49.9 (approximately all 50)
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Cheers,
Stan H.

Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

mean of 60 and a standard deviation of 8.  Sample SD = 8/√50 = 1.1314

 z = (60-36)/1.1314 = -3.3941  NORMSDIST(-3.3941) = .0003

Percentage above 36 = 1 - (percentage below) 

                      1 - .0003 = .9997  0r  99.97% have scores above 36

how many got scores above 36?  Probability of ALL of them is VERY good

 .9997 * 50 = 49.985