Glen wrote: > [EMAIL PROTECTED] (Benjamin Kenward) wrote in message >news:<9vnj9m$s2c$[EMAIL PROTECTED]>... > > Hi folks, > > > > Let's say you have a repeatable experiment and each time the result can be > > classed into a number of discrete categories (in this real case, seven). > > If a treatment has no effect, it is known what the expected by chance > > distribution of results between these categories would be. I know that a > > good test to see if a distribution of results from a particular treatment > > is different to the expected by chance distribution is to use a > > chi-squared test. What I want to know is, is it valid to compare just one > > category? In other words, for both the obtained and expected > > distributions, summarise them to two categories, one of which is the > > category you are interested in, and the other containing all the other > > categories. If the chi-square result of the comparison of these categories > > is significant, can you say that your treatment produces significantly > > more results in particularly that category, or can you only think of the > > whole distribution? > > Yes, as long as the choice of which category to do it for is not based > on the data... no fair just testing the most extreme one.
good advice in every case. Jay > > > Glen -- Jay Warner Principal Scientist Warner Consulting, Inc. 4444 North Green Bay Road Racine, WI 53404-1216 USA Ph: (262) 634-9100 FAX: (262) 681-1133 email: [EMAIL PROTECTED] web: http://www.a2q.com The A2Q Method (tm) -- What do you want to improve today? ================================================================= Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =================================================================
