Sources of Variance
Within Groups Variability
a) differences amoung subjects
b) experimental error
- measurement, recording error
Between Groups Variability
a) differences amoung subjects
b) experimental error
- measurement, recording error
c) variation in your independent variable
Maximizing chances of finding significance
(based on ratio of between group: within group variance)
Increase
Between Group Differences by:·
increasing strength of IV?· changing the level of treatment of IV?
· use a more sensitive operational definition for the DV?
Decrease
Within Group Variance·
increase control over extraneous factors· decrease subject variance
- change design to matched or within subject design
· increase sample size