see also the contributed document by John Verzani, Simple R, page 87f. > Adaikalavan Ramasamy wrote: > > > I would try to construct the confidence intervals and > compare them to > > the value that you want > > > >>x <- rnorm(20) > >>y <- 2*x + rnorm(20) > >>summary( m1 <- lm(y~x) ) > > > > > > <snip> > > Coefficients: > > Estimate Std. Error t value Pr(>|t|) > > (Intercept) 0.1418 0.1294 1.095 0.288 > > x 2.2058 0.1289 17.108 1.4e-12 *** > > <snip> > > > > That says that the slope estimate is 2.2058 with standard error of > > 0.1289. So the approximate 99% CI is 2.2058 +/- 3*0.1289 = (1.819, > > 2.593) which is clearly greater than 1. > > > > > >>summary(m1)[[4]][2,1] + 3* summary(m1)[[4]][2,2] > > > > [1] 2.592629 > > > >>summary(m1)[[4]][2,1] - 3* summary(m1)[[4]][2,2] > > > > [1] 1.819026 > > >
> I think the preferred way of doing this is with confint: > > # 3 sigma limits > confint(m1, parm = "x", level = 1 - pt(-3, m1$df.resid) * 2) > # 95% confidence (default) > confint(m1, parm = "x") > > > For your next question, you simply compare the CI of one slope to > > another and see if they overlap. > > > > There is probably a way to construct proper significance > testing to get > > p-values and such. You can try reading MASS4 or hopefully > someone in the > > list might provide with a neater answer. > > > > > > On Tue, 2004-07-20 at 17:02, Avril Coghlan wrote: > > > >>Hello, > >> > >> I'm a newcomer to R so please > >>forgive me if this is a silly question. > >> > >>It's that I have a linear regression: > >>fm <- lm (x ~ y) > >>and I want to test whether the > >>slope of the regression is significantly > >>less than 1. How can I do this in R? > >> > >>I'm also interested in comparing the > >>slopes of two regressions: > >>fm1 <- lm (x ~ y) > >>fm2 <- lm (a ~ b) > >>and asking if the slope of fm1 is > >>less than the slope of fm2. Is this > >>easy to do in R? > >> > >> > >>I will be very grateful for any help. > >> > >>regards, > >>Avril Coghlan > >>(University College Dublin, Ireland) > >> > >>______________________________________________ > >>[EMAIL PROTECTED] mailing list > >>https://www.stat.math.ethz.ch/mailman/listinfo/r-help > >>PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html >> > > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html -------------------------------------------------------------------------------- The information contained herein is confidential and is inte...{{dropped}} ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
