9 Introduction to Simple Experiments Flashcards
Between-subjects design
Between-groups design.
Carryover effects
Order effect.
Congruent-measures design
An experiment using a within-groups design in which participants are exposed to all the levels of an independent variable at roughly the same time, and a single attitudinal or behavioral preference is the dependent variable.
Condition
One of the levels of the independent variable in an experiment.
Confound
A potential alternative explanation for a research finding (a threat to internal validity).
Control group
A level of an independent variable that is intended to represent “no treatment” or a neutral condition.
Control variable
A potential variable that an experimenter holds constant on purpose.
Counterbalancing
Presenting the levels of the independent variable to participants in different orders to control for order effects.
Demand characteristics
Cues that lead participants to guess a study’s hypothesis or goals.
Design confound
A second variable that happens to vary systematically along with the independent variable and therefore is an alternative explanation for the results.
Independent-groups design
An experimental design in which different groups of participants are exposed to different levels of the independent variable such that each participant experiences only one level of the independent variable.
Latin square
A formal system of partial counterbalancing that ensures that each condition appears in each position at least once.
Manipulation check
An extra dependent variable that researchers can include in an experiment to determine how well an experimental manipulation worked.
Matched-groups design
An experimental design in which participants who are similar on some measured variable are grouped into sets and the members of each match that are then randomly assigned to different experimental conditions.
Order effects
A threat to internal validity that occurs when people exposed to one condition changes how people react to a later condition.
Partial counterbalancing
A method of counterbalancing in which some, but not all, of the possible condition orders are represented.
Pilot study
A study completed before (or sometimes after) the study of primary interest, usually to test the effectiveness or characteristics of the manipulations.
Placebo group
A control group that is exposed to an inert treatment (e.g., a sugar pill).
Posttest-only design
An experiment with an independent-groups design in which participants are tested on the dependent variable only once.
Power
The probability that the study will show a statistically significant results when some effect is truly present in the population.
Practice effect
A type of order effect in which people’s performance improves over time because they become practiced at the depended measure (not because of the manipulation or treatment).
Pretest/posttest design
An experiment with an independent-groups design in which participants are tested on the key dependent variable twice – once before and once after exposure to the independent variable.
Random assignment
The use of a random method (e.g., flipping a coin) to assign participants into different experimental groups.
Repeated-measures design
An experiment with a within-groups design in which participants respond to a dependent variable more than once, after exposure to each level of the independent variable.
Selection effect
A threat to internal validity that occurs when the kinds of participants at one level of the independent variable are systematically different from those at the other level of the independent variable.
Systematic variability
In an experiment, the situation that occurs when the levels of a variable coincide in some predictable way with the experimental group membership, creating a potential confound.
Treatment group
The participants in an experiment who are exposed to the level of the independent variable that involves a drug, therapy, or intervention.
Unsystematic variability
In an experiment, the levels of a variable occurring independently of experimental group membership, contributing to variability within groups.
Within-groups design
Within-subjects design.
A study design in which each participant is presented with all levels of the independent variable.
