Chapter 2 Notes (6/14/10)
Variables:
1.) independent variable: variable that is manipulated in order to establish causation;
must have this variable in order to demonstrate causation
*Fit induscies (spelling?): what’s the statistical probability of models
ex: model 1: X
Y
model 2: Y
X
model 3: X
Z
Y
So if model 1 isn’t very likely, you can cro
ss that one out. Same for model 2. If model 3 is 60% likely, then it is the causal
model.
*Applied = Nonexperimental approach (not as good as experimental approach); in
this the IV = predictor
*Experimental approach is better
2.) dependent variable: the variable you are measuring or observing
*Quantitative measurement: differ in magnitude; ex: reaction time
relationship b/t IV and DV is quantitative
directly related to the dependent variable (the DV has to be a quantitative measurement)
*A qualitative measurement is something that tells us difference in kind NOT in
magnitude; ex: color; brand name of shoes
**But, the IV can be either quantitative or qualitative!!
ex 1:
10mg
20 mg
30mg
?
RT
? RT
? RT
so in ex 1, the # of mg is your IV and the RT value is the D.V.both are quantitative
ex 2:
standard lecture
stimulation
grade on test
grade on test
Summary:
Two types of variables—quantitative and qualitative
*quantitative
usually the D.V. falls under this; I.V. can too
numbers that
reflect magnitude (more of less of something)
*qualitative
often independent variables; occasionally they are dependent
differs in kind
categorical independent variable
Other variables:
3) mediating variable
X—Z—Y
Ex: X is Anxiety (IV)
Y is Test performance (DV)
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 Summer '09
 claffey
 Psychology, Causality, representative, Correlational Studies, extraneous variables, Natural Manipulation Research

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