Nick
Posts:
690
Registered:
10/25/06


Re: Help with probability&stat problem
Posted:
Jun 11, 2007 1:42 PM


"tutorny" <tutorny@gmail.com> wrote in message news:1181583242.453424.219550@c77g2000hse.googlegroups.com... > >> Do you really think there is a 97% chance that >> there will be a 30% drop out rate? Suppose I asked >> you the probability that 100 of the students would >> drop out. How would you calculate that? Do you think >> that is a higher probability than only 30 students >> dropping out? > > I am not entirely sure that I follow. 30 students out of 110 is 27%. > So if a 20% rate is to be expected, isn't it feasible that a 27% rate > is 96% likely? > > If I made the mistake there, it would be in making p = 0.20. So, I > think what you are saying is that p should be = 0.80. But doing the > calculations that way results in a nonsensical answer..
No, there is a 50% probability of there being a dropout rate of greater than 20%. At the extreme of a greater than 27% dropout rate there is likely to be a very small dropout rate ie in the tail of the distribution.
Nick

