I have the probability: P(T+ / D+) i want to find P(T+,D+) which is: P(T+ / D+)*P(D+) and i have those probabilities. i dont know how to write this in R. something like this: (say p2 is the conditional prob. and p1 is the joint prob.)
p2 <- p1/.6 x <- rbinom(200, 1, .6) y <- rbinom(300, 1, .6) if (x) p2==0.95 if (y) p2==0.80 i don't know how to write the "if "condition. thank you for your reply, sigalit. On 8/8/07, Kyle Henderson <[EMAIL PROTECTED]> wrote: > > That depends on what you meant by writing the conditional probability. > Bayes rule says that the probability of testing positive when one has the > disease is calculated as follows: > > Pr(T+ | D+)=(Pr(D+ | T+)*Pr(T+))/Pr(D+) > > is that what you mean? > > > Kyle H. Ambert > Department of Behavioral Neuroscience > Oregon Health & Science University > > > > On 8/8/07, sigalit mangut-leiba <[EMAIL PROTECTED]> wrote: > > > hello, > > i want to do a binomial simulation, by taking 200 var. from one group > > (x) > > and 300 from another (y). > > the prob. for disease=.6 in both groups. > > > > x <- rbinom(200, 1, .6) > > > > y <- rbinom(300, 1, .6) > > if the person is from group x - the probability to find the disease, > > assuming the person is sick, is .95, > > if he is from group Y its .80. > > i want to know the joint probability: p(the person has the disease and > > tested sick)=P(D+,T+). > > my problem is how to write the conditional prob. > > Thanks for your help, also reference on this subject (binomial > > simulation) > > would be great. > > Sigalit. > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@stat.math.ethz.ch mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide > > http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html> > > and provide commented, minimal, self-contained, reproducible code. > > > > [[alternative HTML version deleted]] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
