r - Scheffe Test in R

Question

I have 3 groups: Control, Experimental 1, Experimental 2. I am trying to run a Scheffe Test comparing the means of Experimental Groups 1 & 2 compared to the mean of the Control group.

I have tried a regular ScheffeTest(x=model), but that gives me the comparisons of each group (i.e. Control/Exp1; Control/Exp2; Exp1;Exp2).

How would I be able to compare the means of both experimental groups together with that of the control group?

ScheffeTest(x=model)

  Posthoc multiple comparisons of means : Scheffe Test 
    95% family-wise confidence level

$Morality
                      diff     lwr.ci     upr.ci    pval    
Exp 1-Control     -18.955128 -29.029235 -8.8810211 3.3e-05 ***
Exp 2-Control     -9.908715 -20.352044  0.5346142  0.0672 .  
Exp 1-Exp 2        9.046414  -1.741866 19.8346927  0.1208    

---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

As you can see, it is comparing each group, but I would like to only compare both experimental groups together versus the control

Answer 1

您可以使用参数指定的适当对比度来指定比较contrast。例如，contrasts=matrix(c(-1, 0.5, 0.5), ncol=1)应该将示例中的控件与剩余的两个组进行比较。