FInal Flashcards
Six threats to internal validity
Maturation History Regression to the mean Attrition Testing Instrumentation
Three other threats to internal validity
Observer bias
Demand characteristics
Placebo effect
Neither the experimenters nor the participants knows who is in what group.
Double-blind study
Same as double-blind, plus
The control group receives a placebo, such as a sugar pill, fake therapy, etc.
Double-blind placebo-control study
No significant difference between the levels of the independent variable
null effect
Why might you get a null effect?
- Because there really is no effect!
- The different levels of the independent variable weren’t different enough.
- There was too much unsystematic variability.
Why might the difference between groups be too small?
- Manipulation was not STRONG enough.
- Measure was not SENSITIVE enough.
- Ceiling or floor effects.
everyone is maxed out on the measure
Ceiling effect
- The questions were so hard that people got most of them, even the easy-to-read ones, wrong.
- The anagrams were so hard that a red test cover couldn’t make performance worse.
Floor effect
How might unsystematic variability lead to null results?
- Measurement error
- Individual differences
- Situation noise
is the likelihood that a study will yield a statistically significant result when the IV really has an effect
Power
People adapt to the environment, the conditions on their own. Children get better at walking; trees grow taller; depressed people get better over time; campers get used to the camp and aren’t so wild. Time just passes and things change
Maturation
Something happens to most of the people in the experiment. Weather got colder for the “using electricity” folks. Maybe the campers started a swimming program that tired them out. This is a historical or external event. It isn’t that time went by and things got better (like above). Something happened.
History
The statistical likelihood that things even out. An extreme score at the pretest usually
leads to a regression to the mean on the post score.
Regression to the mean
A reduction in participant numbers that occurs when people drop out before the end of the study
Attrition
The change in the participants as a result of taking the test—they may become better because of practice, or they may be fatigued or bored
Testing
When a researcher uses two different measures, but they don’t capture the same concept, or capture it at different levels. Example: observers change their observation criteria over time, a researcher uses different forms of a test at pretest and posttest and they’re not equivalent forms. The instrument changes from time 1 to time 2
Instrumentation
researchers’ expectations influence their interpretation of the results—or even influence the outcome of the study.
Observer bias
participants guess what the study is supposed to be about and change their behavior in the expected direction.
Demand characteristics
people receive a treatment and really improve - but only because they believe they are receiving a valid treatment.
Placebo effect
A replication study in which researchers repeat the original study as closely as possible to see whether the original effect shows up in the newly collected data.
direct replication
Pertaining to a study whose results have been obtained again when the study was repeated.
replication
A replication study in which researchers replicate their original study but add variables or conditions that test additional questions
replication-plus-extension
A replication study in which researchers examine the same research question (the same conceptual variables) but use different procedures for operationalizing the variables.
conceptual replication
the idea that a meta-analysis might be overestimating the true size of an effect because null effects, or even opposite effects, have not been included in the collection process.
file drawer problem
The extent to which a laboratory experiment is designed so that participants experience authentic emotions, motivations, and behaviors.
experimental realism
Help demonstrate how seemingly basic human processes can work differently in different cultural contexts. And how when theories are tested only on WEIRD people they may not represent everyone.
cultural psychologist
Western, educated, industrialized, rich, and democratic
WEIRD samples
A third variable that changes the relationship between two variables.
moderators