You ask a participant in a study to roll a die,and to keep rolling until they roll either a 5 or a 6.What is the variance of the distribution of the number of rolls required?
A)6
B)3
C)1/3
D)1/18

Question

Quizplus · Accepted Answer

The number of rolls until a 5 or 6 is rolled follows a geometric distribution with success probability p = 1/3 (since there are 2 successful outcomes out of 6 possible outcomes). The variance of a geometric distribution is given by (1-p)/p^2. Substituting p = 1/3 gives (1-(1/3))/(1/3)^2 = (2/3)/(1/9) = 6.

You Ask a Participant in a Study to Roll a Die,and