First, I would recommend not using Excel for statistics. Second, as to your question; I don't know what Excel does. But one possibility is that it is reporting type 3 results; that is, in the second analysis it is reporting the effect of A controlling for B. In this case, there is no reason to expect that the results should be equal because it is a dffierent hypothesis.
HTH Peter Peter L. Flom, PhD Assistant Director, Statistics and Data Analysis Core Center for Drug Use and HIV Research National Development and Research Institutes 71 W. 23rd St www.peterflom.com New York, NY 10010 (212) 845-4485 (voice) (917) 438-0894 (fax) >>> [EMAIL PROTECTED] 3/30/2004 8:18:19 AM >>> I am using Excel to do some ANOVA calculations. Say that we have one independent variable A, where we have 10 samples for each level of A. Then a one way ANOVA tells us whether there is a significant difference in the means of A's levels. If I add a second independent variable B with 2 levels to the data set, and I assign 5 samples from each level of A to each level of B, then each cell of the 2 dimensional table will be made up of 5 samples. When I perform a two way ANOVA in Excel, it gives us 3 values, then means of the samples grouped by factor A, the means grouped by factor B, and the interaction effect. However the p value I get for the samples grouped by A in two way ANOVA, is different than the p value of the one way ANOVA on A that I performed at the beginning. Why is this? Shouldn't the p-values be identical? Aren't we testing the same hypothesis in each case? Thank you very much. . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . ================================================================= . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
