Question 722567: This question is on normal distribution, I need some help understanding how to solve these problems. I am taking a NCPace course through the military and do not have an actual instructor to ask for help.
Determine the answers to the following questions which relate to a sample of students who took a physics test. Their scores were normally distributed with a mean of 70 and a standard deviation of 10. What percentage of students made 90 on the test?
Using the rules of normal distribution my answer would be 1.18%. I just don't know if I am going about solving this the correct way. Thank you in advance.
Respectfully,
STG2(SW/EXW)Purvis, Sarah M. , USN
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! scores were normally distributed with a mean of 70 and a standard deviation of 10. What percentage of students made 90 on the test?
Using the rules of normal distribution my answer would be 1.18%. I just don't know if I am going about solving this the correct way.
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Find the z-score of 90.
z(90) = (90-70)/10 = 2
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Then P(x > 90) = P(z > 2)
Using a TI-84 calculator I get:
P(z > 2) = normalcdf(2,100) = 0.0228 or 2.28%
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Let me know if you need further help.
Cheers,
Stan H.
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