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I wonder if somebody could help me with this probability problem? You are collecting data on the success of a new anti-malarial drug on the incidence of malaria. You compare two samples: a treatment sample, and a control sample. Each sample contains 100 people randomly selected from a capitol city in a country with a high incidence of malaria. In the treatment sample, all 100 people receive the preventative medication. In the control sample, all 100 people receive a placebo. When the trial is over (after one year), you survey the people in both trials and find 7 people in the treatment sample have contracted malaria while 12 people in the control sample have contracted malaria. a) You plan to follow up in 6 months to see how the people who contracted malaria in each group are faring – how many days of work did they miss due to malaria? Because the study was double-blind, you do not know which patients contracted malaria. You call the home phone numbers of 20 people in the treatment group. What is the probability you reach 5 people (out of the 20 people called) who contracted malaria in the treatment group?

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If that is you’re question (without reading the body) I’d probably say: Statistically speaking, yes, someone can. Also (afther reading the body), I wonder why you gave information on the control group. – k.stm Feb 19 '13 at 20:54
up vote 1 down vote accepted

$\frac{\begin{pmatrix} 7 \\ 5 \end{pmatrix} \begin{pmatrix} 93 \\ 15 \end{pmatrix}}{\begin{pmatrix} 100 \\ 20 \end{pmatrix}}$

This distribution is hyper geometric:

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It's a probability Mass Function problem... – user63036 Feb 22 '13 at 3:00
@user63036 Right and the the PMF is given by the hyper-geometric formula. Did you visit the link? – Sean Ballentine Feb 22 '13 at 21:17

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