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Scores of tests form a normal distribution with a mean of 70 and S.D. of 10

Mathematics
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A. What proportion of students score less than 75
B.  If samples of n=4 are selected from the population what proportion will have means less than 75?
C.  If samples of n=75 are selected from the population what proportion will have means less than 75

Nov 15th, 2014

z = (75-70)/10 = 0.5

P (z< 0.5)= 0.6915

Z =(75-70)/(10/2) = 1.0       ; Standard error =10/sqrt(4) =5

P(z<1) = 0.8413

z = (75-70)/(10sqrt(75))=5/(1.1547) = 4.33   ; standard error= 10/sqrt(75)

P (z< 4.33) =1.0000

Nov 15th, 2014

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Nov 15th, 2014
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Nov 15th, 2014
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