A population of scores forms a normal distribution with a mean 80 and a SD of 80

Mathematics
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a. What is proportion of the scores have values between 75 & 80?
b.  For samples of n=4 what proportion of the samples will have means between 75 & 85?
c.  For samples of n=16, what proportion of the samples will have the means between 75 & 85?

Nov 15th, 2014

a

z = 0 when x=80

z= -5/80= -0.0625= -0.06

P(z< -0.06)= 0.5- 0.4760 = 0.024

b.

z= (85-80)/80/2 = 10/80 =0.125=0.12

P(-0.12 < z < 0.12) = 0.0955

c

z= (85-80)/(80/4) =20/80 =0.25

P ( -0.25<z< 0.25)=0.1974

Nov 15th, 2014

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