Hi, The significant interaction between A (continous) and B (categorical) means that the slopes of Y in relation to A are different for classes of B. Since your categorical B was binary, the default reference class (B2) was intecept, and the slope of A for (B2) was 0.0017799. However, the slope of A for another class (B1) was 0.0017799+0.0059008. The test shows that the slopes were significantly different.
HTH Weidong On Wed, Nov 23, 2011 at 12:20 PM, Chen Xiu <chenxiu.worldw...@googlemail.com> wrote: > Hello everyone, > > Recently, I faced a problem on explanatory of *Interaction variable* in > Linear Regression, could anyone give me some help on how to explain that? > > the response variable Y is significantly correlated with *Interaction > variable X* which is consisted of Continuous predictor A and Categorical > predictor B. The Categorical predictor B has two factors B1 (value=1) and > B2 (value=0). The result is as follows: > > Call: > lm(formula = Y ~ ... + *A:B*, data = ..., na.action = na.omit) > > Residuals: > Min 1Q Median 3Q Max > -0.84267 -0.29877 0.01961 0.32187 0.98519 > Coefficients: > Estimate Std. Error t value > Pr(>|t|) > (Intercept) 0.7699265 0.5129588 1.501 0.1408 > BB1 -0.6657700 0.2668956 -2.494 0.0166 * > A 0.0017799 0.0007569 2.352 0.0235 * > ... 0.2393929 0.2334615 1.025 0.3110 > ... -0.3877065 0.2317213 -1.673 0.1017 > *BB1:A 0.0059008 0.0025522 2.312 0.0257 ** > --- > Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 > > Residual standard error: 0.4379 on 42 degrees of freedom > Multiple R-squared: 0.2813, Adjusted R-squared: 0.1958 > F-statistic: 3.288 on 5 and 42 DF, p-value: 0.01354 > > *My questions:* > > 1. *How to explain the result of BB1:A correlated with Y? since BB1 is > only one factor of B, and if it is combined with A, how does the > combination mean?* > 2. *Can I believe the significance of either single BB1 or A? Why?* > > Thank you in advance for any possible help! > > Chen, > > a beginner in R and statistics > > -- > Chen Xiu > > Guest Fellow/ PhD Student > Department of Conservation Biology > UFZ - Helmholtz Centre for Environmental Research > Permoserstr. 15 > D-04318 Leipzig > Germany > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org 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. > ______________________________________________ R-help@r-project.org 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.
