PSYC 270 Exam 2, Part 3
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PSYC 270 Exam 2, Part 3
Advantages of Between-Subjects Designs
Includes a control or comparison group that helps to control for many extraneous variables.
Can randomly assign participants to groups, which helps to balance extraneous variables across the groups.
Disadvantages of Between-Subjects Designs
You can’t always randomly assign participants to groups.
Large individual differences between participants may make it difficult to observe meaningful group differences.
If the subjects are used more than once or matched, this design is called a
Advantages of Within-Subjects Design
They take fewer participants.
They typically have more statistical power (such as a matched t-test)
Disadvantages of Within-Subjects Design
You have to worry about practice effects and carryover effects
equalizing the amount of practice, for example, you could test one person in the B1, B2, B3 order, another with B1, B3, B2, until every order is tested; used to avoid practice and carryover effects
a factorial design in which there is at least one between-subjects factor and at least one within-subjects design
Mixed Designs are useful when:
You might end up testing the subjects too much in a wholly within-subjects design
systematic + nonsystematic variance
"between group" variance; experimental variance due to the IV; due to confounding variables
error variance or variance within the groups; due to chance factors
If between-group variation is not significantly ______ than within-group variance, then group differences probably do not contribute anything beyond chance variability
statistical anaylsis comparing more than 2 sets of scores
Sources of sequence/carryover effects
learning, fatigue, habituation, sensitization, contrast, adaptation
ways to deal with carryover effect
random order; counterbalancing
advantages of matched design
can control for subject variables that may otherwise obscure the effect of the IV
disadvantages of matched design
matching variable needs to be reliable, difficult finding enough participants who are matched, impossible to match on every possible variable that might influence the IV
when greater than 2 IV, we can examine _______ and ______
main effects; interactions
overall effect of one IV (ignoring the other)
effect of one IV depends on the level of a second IV