Variance
nMS = variance (variance is the mean of the squared deviations)
n MS = S2 = SS/df
n MSB = SSb/dfB
n MSw = SSW/dfW
nTwo possible sources of variance exist
1.Treatment Variance - btwn group differs due to treatment
nPossible sources of treatment variance
¤Treatment effect
¤Individual differences
¤Experimenter error
2.Error Variance - wthn treatment group participants receive same manipulation.  If their scores differ it is due to error
nPossible sources of error variance
¤Individual differences
¤Experimenter error