Results

ANOVA

ANOVA - accidents
Cases Sum of Squares df Mean Square F p
alcohol 364.146 2 182.073 469.271 < .001
speed 128.164 2 64.082 165.164 < .001
alcohol ✻ speed 1.911 4 0.478 1.231 .299
Residuals 66.346 171 0.388    
Note.  Type III Sum of Squares

Descriptives

Descriptives plots

Post Hoc Tests

Standard (HSD)

Post Hoc Comparisons - alcohol ✻ speed - Conditional on alcohol
alcohol Mean Difference SE df t ptukey
none none some -0.839 0.197 171 -4.257 < .001
    much -1.782 0.197 171 -9.047 < .001
  some much -0.944 0.197 171 -4.790 < .001
some none some -1.319 0.197 171 -6.696 < .001
    much -2.136 0.197 171 -10.841 < .001
  some much -0.817 0.197 171 -4.145 < .001
much none some -1.216 0.197 171 -6.171 < .001
    much -2.275 0.197 171 -11.550 < .001
  some much -1.060 0.197 171 -5.379 < .001
Note.  P-value adjusted for comparing a family of 3 estimates.
Post Hoc Comparisons - alcohol ✻ speed - Conditional on speed
speed Mean Difference SE df t ptukey
none none some -1.338 0.197 171 -6.790 < .001
    much -3.191 0.197 171 -16.200 < .001
  some much -1.854 0.197 171 -9.410 < .001
some none some -1.818 0.197 171 -9.230 < .001
    much -3.568 0.197 171 -18.114 < .001
  some much -1.750 0.197 171 -8.884 < .001
much none some -1.691 0.197 171 -8.585 < .001
    much -3.684 0.197 171 -18.703 < .001
  some much -1.993 0.197 171 -10.118 < .001
Note.  P-value adjusted for comparing a family of 3 estimates.

ANCOVA

ANCOVA - accidents
Cases Sum of Squares df Mean Square F p
alcohol 403.595 2 201.797 259.608 < .001
weight 59.613 1 59.613 76.691 < .001
Residuals 136.808 176 0.777    
Note.  Type III Sum of Squares

Descriptives

Descriptives - accidents
alcohol N Mean SD SE Coefficient of variation
none 60 2.980 0.888 0.115 0.298
some 60 4.595 1.071 0.138 0.233
much 60 6.461 1.181 0.152 0.183

Descriptives plots

weight - accidents

ANOVA

ANOVA - weight
Cases Sum of Squares df Mean Square F p
alcohol 3114.404 2 1557.202 43.831 < .001
Residuals 6288.355 177 35.527    
Note.  Type III Sum of Squares

Descriptives

Descriptives - weight
alcohol N Mean SD SE Coefficient of variation
none 60 66.758 7.765 1.002 0.116
some 60 76.445 4.611 0.595 0.060
much 60 68.865 5.003 0.646 0.073

Descriptives plots