A loaded die is such that when it is thrown the probability of obtaining a score of six is 0.25.

In 5 throws of the die calculate the probability that:
(I) a six will be obtained for the first time on the last throw.

B) what is the probability that the 5th six occurs on the 15th trial?

Question

A loaded die is such that when it is thrown the probability of obtaining a score of six is 0.25.

In 5 throws of the die calculate the probability that:
(I) a six will be obtained for the first time on the last throw.

B) what is the probability that the 5th six occurs on the 15th trial?

anonymous · Answer

Looks like a negative binomial situation.
Do you know the formula for that?

anonymous · Answer

Can really be done just using multiplication rule, though.

anonymous · Answer

For part (B), you'll first want to calculate the probability of getting 4 sixes in 14 trials.

anonymous · Answer

First part I've sorted now :)
So for part B once you've worked out the probability of getting 4 sixes in 14 trials do you add it to the probability of getting one 1 six on the 15th trial?

anonymous · Answer

No, just multiply it by the probability of getting a six one more time.

anonymous · Answer

Awww that's great - thanks for your help :)