edited by
604 views
0 votes
0 votes
A dice is tossed thrice. A success is getting ‘1 or 6' on a toss. Find the variance of number of successes _. 
Answer  0.66
edited by

1 Answer

Best answer
2 votes
2 votes
No. of successes:     0                          1                                 2                                  3

Probability:             8/27                   12/27                          6/27                            1/27

E(X) = 0(8/27) + 1(12/27) + 2(6/27) + 3(1/27) = 27/27 = 1;

E(X^2) = 0^2(8/27) + 1^2(12/27) + 2^2(6/27) + 3^2(1/27) = 45/27

V(X) = E(X^2) - [E(X)]^2

V(X) = 45/27 - (1)^2 = 45/27 -1  = 18/27 = 0.66
selected by

Related questions

0 votes
0 votes
0 answers
1
Magma asked Jan 14, 2019
548 views
Number of ways we can distribute 5 red balls , 5 white balls and 5 blue balls into 3 different boxes ?
0 votes
0 votes
1 answer
2
0 votes
0 votes
1 answer
4
Chhotu asked Dec 1, 2017
472 views
Hi Guys,I think final answer of following question should be 0.47. Please correct me if i am wrong.