Question 1157631
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What is a passing score out of ten questions?


The probability of at least *[tex \Large k] successes in *[tex \Large n] trials where the probability of success on any given trial is *[tex \Large p] is given by:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ P(\geq{k},n,p)\ =\ \sum_{r\,=\,k}^n\,{{n}\choose{r}}\,p^r\,(1\,-\,p)^{n-r}]


Your *[tex \Large n] is 10, and your *[tex \Large p] is 0.2, but you don't know *[tex \Large k], which is the number that represents a passing score.


So for example, if you have to get six correct to pass, your calculation would be:


*[tex \LARGE \ \ \ \ \ \ \ \ \ \ P(\geq{6},10,0.2)\ =\ \sum_{r\,=\,6}^{10}\,{{10}\choose{r}}\,(0.2)^r\,(0.8)^{10-r}]


Change *[tex \Large k] if the number to pass is different than six.
								
								
John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
<img src="http://c0rk.blogs.com/gr0undzer0/darwin-fish.jpg">
*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \  
								
{{n}\choose{r}}
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