Contrasts Flashcards
1
Q
What is the procedure for determining contrast coefficients when the sample sizes are equal?
A
- Divide the samples into 3 groups, corresponding with H0.
- ck = 0 for all groups that do not participate.
- ck = 1 for all groups that participate on one side of H0.
- ck = -1 for all groups that participate on the other side of H0.
2
Q
what is the procedure for determining contrast coefficients when the samples sizes are not equal.
A
- divide the samples into 3 groups, corresponding with H0.
- ck = 0 for all groups that do not participate.
- ck = [formula] for all group on one side of H0.
- ck = - [formula] for all groups on the other side of H0.
3
Q
Which contrasts are used in this course?
A
- a priori contrasts: planned contrasts, Helmert and trend analysis.
- post hoc contrasts: Tukey and Scheffé
4
Q
What is the syntax for planned contrasts?
A
UNIANOVA BY group /CONTRAST (group) = Special ( ck, -ck) /METHOD = SSTYPE(3) /INTERCEPT= INCLUDE /CRITERIA = ALPHA (0.05) /DESIGN = group
5
Q
Explain orthogonal contrasts.
A
all contrasts are uncorrelated.
- SSb represents dispersion of means
- contrast explains part of the dispersion of means.
contrasts are orthogonal when
ck1ck2 = 0 // (ck1ck2)/nk = 0
6
Q
What is the syntax for Helmert contrasts?
A
UNIANOVA BY group /CONTRAST (group) = HELMERT /METHOD = SSTYPE(3) /INTERCEPT = INCLUDE /CRITERIA = ALPHA (0.05) /DESIGN = group
7
Q
What is the syntax for Trend Analysis contrasts?
A
UNIANOVA BY group /CONTRAST (group) = Polynomial /METHOD = SSTYPE(3) /INTERCEPT = INCLUDE /CRITERIA = ALPHA (0.05) /DESIGN = group
8
Q
What is the syntax for Tukey contrasts?
A
UNIANOVA BY group /METHOD = SSTYPE(3) /INTERCEPT = INCLUDE /POSTHOC = group(TUKEY) /CRITERIA = ALPHA (0.05) /DESIGN = group
9
Q
What is the test procedure for Scheffé?
A
- hypotheses
- critical value Fcv
- Fcontrast > (K-1)xFcv
- conclusion
10
Q
What is the syntax for Scheffé contrasts?
A
UNIANOVA BY group /CONTRAST = (group) Special (ck, -ck) /METHOD = SSTYPE(3) /INTERCEPT = INCLUDE /CRITERIA = ALPHA (0.05) /DESIGN = group