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# Calculate Variance of X. V(X)?

In a shooting workout, a basketball player will keep shooting until he makes 10. If the probability that he makes a shot is 0.7, and X let be the total number of shots he will take, calculate. V(X)=?

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- Randy PLv 72 years agoFavorite Answer
What probability distribution describes "number of trials needed until an event happens k times"?

Answer, which you should know, is "the negative binomial distribution".

So you want to open your text, find the variance of a negative binomial distribution in terms of p, the probability of the event happening, and k the number at which you stop, and then plug the numbers into the formula for that variance.

- Anonymous2 years ago
I know so.

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