PSYC 4703: Experimental
Exam 3 – Chapters 10-13
Content Map
Ch 10 Experimental Research: The simple experiment
3 properties of well-designed experiments
Vary at least one IV
Levels of IV
Experimental and control groups
Assessing manipulation of IV
Pilot test
Manipulation check
Power
Equivalent groups
Random assignment
Conflicts between power and other research goals
Control
Systematic variance
Treatment variance
Confound variance
Analyzing Experimental Data
Random error
Hypothesis testing
Null hypothesis
Experimental hypothesis
Type 1 error
Type 2 error
Beta
Alpha
t- test: is the difference between groups larger than would be expected by chance
alone?
Ch 11 Expanding the simple experiment
Advantages of using more than 2 values of an IV
More than 2 kinds of treatment
Increasing external validity
Improving Construct validity
Analyzing Data from multi-group experiments
ANOVA: basic logic
Within groups variability
Between groups variability
Why not a series of t-tests?
Reading an ANOVA summary table
Degrees of Freedom
F value
Ch 12 Factorial Designs
Benefits of factorial designs
Information yielded by factorial design
Simple main effects
Overall main effects
Interaction effects
How to calculate different effects
Interactions and moderating variables
Potential results of a factorial experiment
Analyzing results
Degrees of freedom
F value
Interpreting main effects
Interpreting interactions
Hybrid designs – studying non-experimental factors
Limitation
Reasons to use
Ch 13
Matched pairs design
Procedure
Considerations
Effective matching variable
Power & the dependent groups t-test
External validity
Construct validity
Data analysis: dependent groups t-test
Repeated measures designs
Considerations
Power
Order effects
Practice
Fatigue
Carry-over
Sensitization
Randomized within subjects design
Procedure
Analysis of data
Counterbalanced within-subjects design
Advantages and disadvantages
Procedure
Analysis
Mixed design
Choosing the right design (table 13-11)
One IV
More than one IV
Possible short essay questions
Ch. 10
1. See questions at the end of the chapter.
2. Compare and contrast the experimental and null hypotheses.
3. Explain why the need for random assignment means that some hypotheses can not be
tested in a simple experiment.
4. Explain why null results do not prove the null hypothesis.
5. Define Type I error, describe what can be done to reduce the risk of making Type I
errors, and explain the tradeoff involved in trying to reduce Type I errors.
6. Define Type II error. Define power. Then, discuss the relationship between Type II
error and power.
7. Contrast Type II errors with Type I errors.
8. Explain the trade-off between power and external validity, construct validity, and
ethics.
9. Describe the basic idea behind the t-test.
Ch. 11
1. Explain the advantages of a multiple group experiment.
2. Define within-group variability and between-group variability. Compare and contrast
within-groups variability and between-groups variability.
3. Explain why, all other things being equal, the greater the variability between group
means, the greater the chance that the treatment had an effect.
4. Explain why you should not use t tests to analyze the results of multiple group
experiments.
5. Describe what a statistically significant F for the treatment effect indicates in a
multiple-group experiment. State two important questions that are not answered by
obtaining a significant F for the treatment effect.
Ch 12
1.
Define factorial experiment. Contrast factorial experiments with the multiplegroup experiments discussed in Chapter 11.
2.
Produce a 2 x 2 factorial experiment studying the effects of chocolate
consumption and listening to music on test performance.
3.
Explain how your 2 x 2 factorial experiment could yield each of the following:
a. four simple main effects;
b. two overall main effects (in your explanation, (a) define main effect and (b)
explain how overall main effects can be estimated from simple main effects);
and
c. an interaction (in your explanation, (a) define interaction and (b) explain how
the interaction can be estimated from simple main effects).
4.
Describe, in your own words, what an interaction is. Give an example of an
interaction.
5.
Describe the relationship between interactions and moderating variables.
6.
Describe the relationship between interactions and external validity.
7.
Distinguish between ordinal and disordinal interactions. Explain why ordinal
interactions may be the result of having ordinal data.
8.
9.
Devise a factorial experiment by adding a potential moderating variable to a
simple experiment (you may use the simple experiment referred to in the previous
objective). Describe, using the terms main effects and interaction, a pattern of
results that would support the idea that you found a moderating variable. Explain
the value of finding a moderator factor.
Describe the main limitation of using a non-experimental variable in a study.
Ch 13
1.
Explain why the matched pairs design has (a) as much internal validity as a simple
experiment and (b) more power than a simple experiment.
2.
Describe the steps involved in creating a matched-pairs design.
3.
Explain the following statement, “with a matched-pairs design you cannot use a
regular between-subjects t test.”
4.
Describe the advantages and disadvantages of using a matched-pairs design.
5.
How does a within-subjects design increases power?
6.
Illustrate the impact of order on the internal validity of a within-subjects design.
Include a discussion of each of the following in your response:
a. practice effects
b. fatigue effects
c. treatment carryover effects
d. sensitization.
7.
How can order effects be minimized? Include a discussion of each of the
following in your response:
a. minimizing each of the four sources (practice, fatigue, carryover, and
sensitization) of order effects,
b. minimizing the number of conditions,
c. balancing out order effects.
8.
Distinguish between a randomized within-subjects design and a matched-pairs
design. Be sure to address randomization, analysis of data, power, order effects,
and external validity.
9.
What is the difference between sequence effects and order effects?
10.
Describe the advantages and disadvantages of counterbalancing.
11.
You want to compare two levels of an independent variable. When should you
choose to use each of the following?
a. matched-groups design
b. pure within-subjects design
c. 2 x 2counterbalanced design
d. simple (two-group, between-subjects) experiment.
12.
You want to examine the effects of two independent variables. Explain when you
should choose to use each of the following:
a. within-subjects factorial design
b. between-subjects factorial design
13.
List three criteria that you could use to determine whether a factor should be a
between-subjects factor or a within-subjects factor.