On Fri, 2007-05-11 at 00:14 +0100, [EMAIL PROTECTED] wrote: > Hi, > > on a > > summary(lm(y~x)) > are the computed t-values for two.sided or one.sided. By looking on some > tables they seem like they are for two.sided.
Yep. > Is it possible to have them > for one.sided? If this makes sense... Yep. Using the example model 'lm.D9' from ?lm: summ.lm <- summary(lm.D9) > summ.lm Call: lm(formula = weight ~ group) Residuals: Min 1Q Median 3Q Max -1.0710 -0.4938 0.0685 0.2462 1.3690 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 5.0320 0.2202 22.850 9.55e-15 *** groupTrt -0.3710 0.3114 -1.191 0.249 --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 0.6964 on 18 degrees of freedom Multiple R-Squared: 0.07308, Adjusted R-squared: 0.02158 F-statistic: 1.419 on 1 and 18 DF, p-value: 0.249 Now get the one sided values: > pt(coef(summ.lm)[, 3], summ.lm$df[2], lower = FALSE) (Intercept) groupTrt 4.773564e-15 8.754884e-01 > pt(coef(summ.lm)[, 3], summ.lm$df[2], lower = TRUE) (Intercept) groupTrt 1.0000000 0.1245116 See ?summary.lm, ?coef and ?pt HTH, Marc Schwartz ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.