It may come a time before the pchisq() function had the lower.tail argument. In those days you had the compute the upper tail as 1-pchisq(x2, df). For any eps<2.2e-16 (.Machine$double.eps), 1-eps==1 so 1-(1-eps)==0 so you would get, e.g., > 1-pchisq(100,2) [1] 0 and people would say 'but the p-value is not 0: it may be very small but not zero' so anova's printing functions would say "<2.2e-16" to mollify them.
Now we have the lower.tail=FALSE argument > pchisq(100,2,lower.tail=FALSE) [1] 1.92875e-22 and don't need the "<2.2e-16" but no one has seen fit to change things. Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, May 7, 2014 at 7:02 AM, Michael Friendly <frien...@yorku.ca> wrote: > Where does the value 2.2e-16 come from in p-values for chisq tests such as > those > reported below? > >> Anova(cm.mod2) > Analysis of Deviance Table (Type II tests) > > Response: Freq > LR Chisq Df Pr(>Chisq) > B 11026.2 1 < 2.2e-16 *** > W 7037.5 1 < 2.2e-16 *** > Age 886.6 8 < 2.2e-16 *** > B:W 3025.2 1 < 2.2e-16 *** > B:Age 1130.4 8 < 2.2e-16 *** > W:Age 332.9 8 < 2.2e-16 *** > --- > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 >> > > -- > Michael Friendly Email: friendly AT yorku DOT ca > Professor, Psychology Dept. & Chair, Quantitative Methods > York University Voice: 416 736-2100 x66249 Fax: 416 736-5814 > 4700 Keele Street Web: http://www.datavis.ca > Toronto, ONT M3J 1P3 CANADA > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
