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Apr 17, 2019 at 12:01 vote accept sam_rox
Oct 25, 2018 at 10:43 history edited kjetil b halvorsen
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Jan 14, 2018 at 17:11 history edited kjetil b halvorsen
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Apr 22, 2017 at 22:49 answer added Dilip Sarwate timeline score: 1
Apr 22, 2017 at 15:32 review Close votes
Apr 22, 2017 at 22:01
Apr 22, 2017 at 15:10 answer added kjetil b halvorsen timeline score: 1
Mar 12, 2017 at 3:22 comment added sam_rox @MichaelHardy Thank you for the explanation. This was from a article and they have obtained $E(K)={1\over\beta}$. For this to happen it should be $\Pr(K=k) = (1-\beta)^{k-1}\beta \text{ for } k = 1,2,3,\ldots;$ and not $P(K=k)=(1-\beta)^k\beta ; k=1,2,3,...$
Mar 12, 2017 at 2:55 comment added Michael Hardy If $K$ is the number of independent trials needed to get one success, with probability $\beta$ of success on each trial, then the event $K\ge k$ is the same as the event of failure on the first $k-1$ trials; therefore $\Pr(K\ge k) = (1-\beta)^{k-1}. \qquad$
Mar 12, 2017 at 2:52 comment added Michael Hardy You need $\Pr(K=k) = (1-\beta)^{k-1}\beta \text{ for } k = 1,2,3,\ldots;$ with $k$ rather than $k-1$ in that exponent, the probabilities will not add up to $1. \qquad$
Mar 12, 2017 at 2:51 comment added Michael Hardy To say that $X$ is exponentially distributed with expected value $1$ is equivalent to saying $\Pr(X>x) = e^{-x}$ for $x\ge0.$ That's a somewhat simpler expression than that for $\Pr(X\le x).\qquad$
Mar 12, 2017 at 2:36 history edited Michael Hardy CC BY-SA 3.0
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Mar 11, 2017 at 23:37 history asked sam_rox CC BY-SA 3.0