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[sir-study-alot]

HSC 2007 QUESTION 25

D II)

if 150 students sat for test 2 , how many students would you expect to have scored less than 64?

mean = 58
std. deviation = 6.0

thanks in advanced

 

[sir-study-alot]

bump this question is pissing me off ..

 

[wayne_d]

Percentage of students who scored less than 64=50%+34%
=84%

therefore 84% of 150 students is equal to (84/100)x150=126

126 students would have scored less than 64

 

[wayne_d]

since x (mean) is equal to 58 and the standard deviation is equal to 6-
x-s=52
x+s=64
x-2s=46
x+2s=76
x-3s=40
x+3s=76

therefore 64 is 1 (one) standard deviation above the mean from x+s, so 50%+34%(one standard deviation above)= 84%

the mean is the central line on the normal distribution curve which is 50%(58)

hope this helps

 

[sir-study-alot]

thanks + rep.