Let X be a b (1, 1/2)RV, and consider all possible random samples of size 3 on X. Compute X bar and S2 for each of the eight samples, and compute the PMFs of X bar and s2
Let X be Bernaulli random Variable with probability p = 1/2 ( i.e. Binomial random variables with n=1 and p=1/2).
The probability mass function of X is
Let Xbar and S2 be sample mean and sample variance respectively.
We have to draw sample of size 3 ( n=3)
The possible samples are ( 0,0,0) , ( 0, 0, 1) , ( 0, 1, 0), ( 0, 1, 1), ( 1, 0 ,0 ) , (1,1,0) ,(1, 0, 1) , (1,1,1).
Sample No. | 1 | 2 | 3 | Xbar | S2 |
1 | 0 | 0 | 0 | 0 | 0.0000 |
2 | 0 | 0 | 1 | 0.3333 | 0.3333 |
3 | 0 | 1 | 0 | 0.3333 | 0.3333 |
4 | 0 | 1 | 1 | 0.6667 | 0.3333 |
5 | 1 | 0 | 0 | 0.3333 | 0.3333 |
6 | 1 | 0 | 1 | 0.6667 | 0.3333 |
7 | 1 | 1 | 0 | 0.6667 | 0.3333 |
8 | 1 | 1 | 1 | 1 | 0.0000 |
From table Xbar take 4 values 0, 0.3333, 0.6667, 1
and S2 take 2 values 0 and 0.3333.
The probability mass function ( PMF) of Xbar is
Xbar | 0 | 0.3333 | 0.6667 | 1 | Total |
P(Xbar) | 1/8 | 3/8 | 3/8 | 1/8 | 1 |
The probability mass function S2 is
S2 | 0 | 0.3333 | Total |
P(S2) | 2/8 | 6/8 | 1 |
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