I am sorry if this is duplicate - I couldn't find exactly what I was looking for anywhere else and have not used multiple regression in quite some time.
I have a data set with one dummy variable using '0' and '1' as the two levels. I only have one other predictor, which I have chosen to input as an interacting factor. The dummy variable indicates a within-subjects condition, and the other predictor is rate of responding (I work with rats). I believe that the rate of responding should be interacting with the condition so that in one condition (dummy variable = 0), the predictor should significantly predict the response variable, while in the other condition (dummy = 1) the numeric predictor should not have a relationship to the response variable. I will show my code for visual reference - I am using R:
reg <- lm(response ~ condition*rate, data = regData) summary(reg)
My output shows that I have a significant intercept and that the numerical predictor's slope is also significant. The interaction factor is not significant. What does the significant intercept value mean in this case? Does it mean that the dummy variable '0' condition is significantly impacting the response variable, while dummy variable '1' does not? Since the interaction is also not significant, should that mean that the dummy and numerical predictors do not interact with each other? I will show output for visual reference:
Call: lm(formula = response ~ condition * rate, data = regData) Residuals: Min 1Q Median 3Q Max -20.982 -8.933 -1.464 6.245 31.196 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 30.543 9.548 3.199 0.00451 ** condition -13.086 14.246 -0.919 0.36929 rate 12.095 4.628 2.614 0.01663 * condition:rate 27.724 15.815 1.753 0.09491 . --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 15.3 on 20 degrees of freedom Multiple R-squared: 0.4488, Adjusted R-squared: 0.3661 F-statistic: 5.428 on 3 and 20 DF, p-value: 0.006762
I apologize I am not the best with regression; thank you in advance for your time. Please let me know if I should clarify anything above.