My knowledge on two-way ANOVAs is a bit shaky so I'm hoping for some clarification. So it appears my overall model is significant (p < 0.0001). However, I am a bit confused why pressure is nonsignificant and temperature is significant in the Type III ANOVA table. Yet individual levels of pressure are significant and temperature 270 has no values. Are these the difference between main effects and simple effects?
Furthermore, I was going to look at pairwise comparisons, but it that wrong when there is no interaction? That is, I can't really control for temperature when comparing different pressure levels and vise versa.
Data
DATA DATA.Temp;
input Pressure Temp Strength @@;
datalines;
120 250 9.60 120 260 11.28 120 270 9.00
130 250 9.69 130 260 10.10 130 270 9.57
140 250 8.43 140 260 11.01 140 270 9.03
150 250 9.98 150 260 10.44 150 270 9.80
;
RUN;
Model Procedure
PROC GLM data = DATA.Temp plots = ALL;
class pressure temp;
model strength = pressure temp / clparm noint solution;
means pressure temp / hovtest = Levene;
lsmeans pressure temp / pdiff = all adjust = Tukey;
RUN;
Output
|
Source
|
DF
|
Sum of Squares
|
Mean Square
|
F Value
|
Pr > F
|
|
Model
|
6
|
1164.195417
|
194.032569
|
540.51
|
<.0001
|
|
Error
|
6
|
2.153883
|
0.358981
|
|
|
|
Uncorrected Total
|
12
|
1166.349300
|
|
|
|
|
Source
|
DF
|
Type III SS
|
Mean Square
|
F Value
|
Pr > F
|
|
Pressure
|
3
|
0.58069167
|
0.19356389
|
0.54
|
0.6727
|
|
Temp
|
2
|
4.65765000
|
2.32882500
|
6.49
|
0.0316
|
|
Parameter
|
Estimate
|
|
Standard
Error
|
t Value
|
Pr > |t|
|
95% Confidence Limits
|
|
Pressure 120
|
9.482500000
|
B
|
0.42366293
|
22.38
|
<.0001
|
8.445834157
|
10.519165843
|
|
Pressure 130
|
9.309166667
|
B
|
0.42366293
|
21.97
|
<.0001
|
8.272500824
|
10.345832510
|
|
Pressure 140
|
9.012500000
|
B
|
0.42366293
|
21.27
|
<.0001
|
7.975834157
|
10.049165843
|
|
Pressure 150
|
9.595833333
|
B
|
0.42366293
|
22.65
|
<.0001
|
8.559167490
|
10.632499176
|
|
Temp 250
|
0.075000000
|
B
|
0.42366293
|
0.18
|
0.8653
|
-0.961665843
|
1.111665843
|
|
Temp 260
|
1.357500000
|
B
|
0.42366293
|
3.20
|
0.0185
|
0.320834157
|
2.394165843
|
|
Temp 270
|
0.000000000
|
B
|
.
|
.
|
.
|
.
|
.
|
