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Rの備忘録

3 回表が出るまでに 9 回以上裏が出る確率

> 1 - pnbinom(8, size=3, prob = .5)
[1] 0.03271484
> pnbinom(8, siz = 3, pro = .5, low = F)
[1] 0.03271484

> sum(dnbinom(9:100, size=3, prob = .5))
[1] 0.03271484

上側の確率が、そのつど重複して加算されている。

> sum(pnbinom(8:10, size=3, prob = .5, lower = F))
[1] 0.06323242

> pnbinom(9, size=3, prob = .5)
[1] 0.9807129
> pnbinom(10, size=3, prob = .5)
[1] 0.9887695

> dnbinom(10, size=3, prob = .5)
[1] 0.00805664

> pnbinom(9, size=3, prob = .5, low =T ) + 
        dnbinom(10, si = 3, pro = .5)
[1] 0.9887695