Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
In Class Assignment 1
Random order of presentation
Counterbalancing
Latin square design (a form of counterbalancing dont worry about it)
Random Order versus Counterbalancing
Random Order: The order is determined randomly for each participant
Order is then
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Study Aid 2
Other forms of validity: Face Validity
Does the measurement procedure look as if it measures what it's supposed to
measure?
Face validity itself is of no great value (unless for political/practical reasons),
but .
Other forms of validity: Cont
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Study Aid 1
A Deep Theoretical Issue
I want to measure a persons alertness
I measure their reaction time in milliseconds to a warning signal
Time is certainly measured on a ratio scale: Equal intervals plus true zero
Can I say that I have a ratio scale me
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Quiz 2 Study Guide
Two Kinds of Interactions
1. A crossover interaction
The lines have opposite slopes (one positive, one negative)
With crossover interactions, the lines will actually cross in at least one
representation of the data.
2. A noncrossove
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Lecture Notes 5
Nominal Scales
A naming scale
Each number reflects an arbitrary category label rather than an amount of a
variable
The numbers have only the property of identity
Comparing relative magnitude is meaningless
This is the very simplest kind of
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Lecture Notes 4
Extraneous variables may be constants. They may then limit generalizability,
but otherwise cause no trouble
Extraneous variables may vary randomly across consitions. They then reduce
power (increase noise, make it harder to detect effects)
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Lecture Notes 3
Some relationships are causal, some are correlational
Causality: What does it mean
David Hume: X causes Y if, in the presence of X, Y always occurs, and in the
absence of X Y never occurs. We can refer to these as the "factual" and
"counte
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Lecture Notes 2
Varieties of Models
Models come in several forms. From the rather vague to the very explicit:
(a) Verbal descriptions
(b) Flow charts and influence diagrams
(c) Mathematical equations
(d) Computer programs
Consider a computer model for exa
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Lecture Notes 1
Research is Based on Empiricism
For an empiricist, the ultimate source of knowledge is observed data
Research is Based on Rationalism
Empiricism alone does not provide "understanding"
Rationalism: a logical framework within which the empir
Design and Interpretation of Psychological Research
PSYC 530

Fall 2012
Study Aid 3
Variance in Independent Groups Designs
Total variance = systematic variance + nonsystematic variance
Systematic variance consists of variance among the independent groups
Called betweengroup variance
Nonsystematic variance (error variance) co