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A fair die is rolled 100 times; obtaining an even number counts as a success. What is the variance of the number of successes?
- 10
- 25
- 18
- 12.5
Correct answer: 25
Solution
For a binomial with n=100, p=1/2, variance = n*p*q = 100*(1/2)*(1/2) = 25.
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