A population consists of the four numbers 3,7,11,15.Consider all possible samples of size two which can be drawn with replacement from this population
Number N= N!/n!(N-n)!
=4!/2!(4-2)!
=(3*4)/2 =6
N=6
samples are
3,7
3,11
3,15
7,11
7,15
11,15
mean =(3+7+11+15)/4 =36/4=9
the mean is 9
standard deviation= sqrt{1/3((3-9)2 +(7-9)2 +(11-9)2 +(15-9)2}
= sqrt{1/3(36+4+4+36)}
= sqrt{1/3(80)}
=5.164
standard deviation is 5.164
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