SOLUTION: A random sample of 100 students who took a statistics exam were asked their score on the exam. The mean score on the test was 50; the standard deviation was 10. The scores are no

Question 126062: A random sample of 100 students who took a statistics exam were asked their score on the exam. The mean score on the test was 50; the standard deviation was 10. The scores are normally distributed.
A) What percent of the students scored below 30?
B) What percent scored between 30 and 55?

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A random sample of 100 students who took a statistics exam were asked their score on the exam. The mean score on the test was 50; the standard deviation was 10. The scores are normally distributed.
A) What percent of the students scored below 30?
Find the t-score 30
t(30) = (30-50)/10 = -2
Find Prob(t<-2); you get 0.0241..
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B) What percent scored between 30 and 55?
t(55) = (55-30) / 10 = 2.5
t(30) = (30-30) / 10 = 0
P(0 < t < 2.5) = 0.4929..
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Cheers,
Stan H.
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