problem-11.16
problem-11.16
We need to compare the following
> summary(lm(Speed ~ factor(Expt),data=morley))
...
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 909.0 16.6 54.76 < 2e-16 ***
factor(Expt)2 -53.0 23.5 -2.26 0.02625 *
factor(Expt)3 -64.0 23.5 -2.73 0.00763 **
factor(Expt)4 -88.5 23.5 -3.77 0.00028 ***
factor(Expt)5 -77.5 23.5 -3.30 0.00136 **
To the output of TukeyHSD()
> TukeyHSD(aov(Speed ~ factor(Expt), data=morley))
Tukey multiple comparisons of means
95% family-wise confidence level
Fit: aov(formula = Speed ~ factor(Expt), data = morley)
$"factor(Expt)"
diff lwr upr
2-1 -53.0 -118.28 12.28
3-1 -64.0 -129.28 1.28
4-1 -88.5 -153.78 -23.22
5-1 -77.5 -142.78 -12.22
3-2 -11.0 -76.28 54.28
4-2 -35.5 -100.78 29.78
5-2 -24.5 -89.78 40.78
4-3 -24.5 -89.78 40.78
5-3 -13.5 -78.78 51.78
5-4 11.0 -54.28 76.28
The latter flags 4-1, 5-1 and 5-4. The
marginal tests find that all the means are different from the reference
level 1.