GLM - 031:010 Research Methods in Psychology Spring 2010...

031:010 - Research Methods in Psychology – Spring, 2010 – March 23
rd
1

Outline

The General Linear Model
True Score Theory (revisited)
“Additive Adjustments”
experiment equations
two types of factor
2

GLM roots –
True Score Theory

True Score Theory
observed value (X) = T + error
if we take many measures of the same thing
while holding everything constant,
then any variability in X is due to the random error,
because T is assumed to be constant
remember: T can only be assumed to be constant
if everything else is constant
3

GLM roots –
True Score Theory

True Score Theory
observed value (X) = T + error

Infinite (possible) influences (or “adjustments”)
error = sum of myriad sub-errors
(
this is why it is often safe to assume that error is Normal
)

X = T + A(e1) + A(e2) + A(e3) + … + A(e ∞ )
4


True Score Theory
observed value (X) = T + error

Infinite (possible) influences (or “adjustments”)
error = sum of myriad errors
but we make no distinctions between the sub-errors
so we continue to treat them as one thing

X = T + error
5
GLM roots –
True Score Theory