1. Chapter 9: Differences among Groups
SFM 651:
Research Methods
Dr. Johnson

2. T tests Between sample and mean Between independent groups
Between dependent groups

3. Sample and mean Is a specific sample different than the mean.
Degrees of freedom
N N is number pf participants
Use a t-table to decide pg 453
If T is greater than the number shown, it is significant.

4. Independent T test 2 samples differ from each other
Most common type of T test
Degrees of freedom N1 + N2 - 2

5. Effect size Degree to which a treatment influenced the outcome
(M1 – M2) / s
M is mean
S is standard deviation
0.8 or greater is large

6. Dependent T test Difference between 2 sets of data
Degrees of Freedom – N-1

7. tails 1 tailed T test 2 tailed T test Can only go in one direction
Can only favor one side – yes or no
2 tailed T test
Can go in both directions
Could favor either side

8. Variance True variance Error variance
Portion of the difference in scores that is real
Error variance
Portion of the difference that is caused by participant variability

9. T vs R
R represents the relationship between the independent and dependent variable
T test can evaluate the reliability (significance) or the relationship

10. Analysis of Variance ANOVA ABC method
Test that allows the evaluation of the null hypothesis between 2 or more groups
ABC method
A – square each participants score -> sum these scores
B – Sum all scores -> Square the sum -> divide by number of participants
C – Sum all scores in 1 -> square the sum -> divide by # participants…..same for 2….3…etc -> add all sums

11. Factorial ANOVA There is more than 1 independent variable
The more comparisons we do, the more we can tell differences

12. Repeated measures ANOVA
Same individual, measured at different points
Throwing distance of a child over a 2 year period
How do they differ
Do they differ

13. Other types ANCOVA MANOVA Analysis of Covariance
A combination of regressions and ANOVA
Adjusts the dependent variable for a covariate
A distractor
MANOVA
Multivariate Analysis of Variance
More than 1 dependent variable