> What seems very silly about this latest spat is that > Jack showed the > exact test, and made the comparison to the > approximation that the OP had > used. Luis has used a different approximation, and > come to a slightly > different answer. > > But you both appear to agree on the exact > calculation. > > Bob > > -- > Bob O'Hara > > Dept. of Mathematics and Statistics > P.O. Box 68 (Gustaf Hällströmin katu 2b) > FIN-00014 University of Helsinki > Finland > > Telephone: +358-9-191 51479 > Mobile: +358 50 599 0540 > Fax: +358-9-191 51400 > WWW: http://www.RNI.Helsinki.FI/~boh/ > Journal of Negative Results - EEB: > http://www.jnr-eeb.org
Bob, what this shows is that with a p of 0.20, the binomial distribution is too assymetrical to be effectively approximated by a symmetrical normal distribution, either with a mean of 22 or 22.5. The Poisson would probably give a much better approximation.