Variables
the researcher assigns participants to a particular level of the variable
Manipulated variable
alternative explanations that can threaten internal validity
Confound
presenting levels of the IV to participants in different orders
counterbalancing
different groups of participants placed at different levels of the IV
Independent-groups design (aka between-subjects)
when participants pick up on cues that lead them to guess the experiment’s hypothesis
demand characteristic
The researcher records what happens in terms of behavior or attitudes based on self-report, behavioral observations, or physiological measures.
Measured variable
when a second variable varies systematically along with the IV and provides an alternative explanation for the results.
Design confound
assigning participants to levels of the IV such that each participant has an equal chance of being in each group.
Random assignment
each participant is presented with all levels of the IV
Within-groups design (aka within-subjects designs)
when there is contamination carrying over from one condition to the next
Carryover effects
The ___________ variable is what I manipulate. The __________ variable is what I observe or measure.
Independent; dependent
when the participants in one level of the IV are systematically different than the participants in the other level or levels of the IV.
Selection effect
When the sample size is small, we can avoid selection effects with
matching
participants are randomly assigned to at least two different groups and are tested on the key dependent variable twice—once before and once after exposure to the independent variable.
pretest/posttest design
How do experiments provide supporting evidence for temporal precedence?
Experiments unfold over time.
any variable that an experimenter holds constant
Control variable
When being exposed to one condition affects how participants respond to other conditions
Order effects
is a simple study, using a separate group of participants, that is completed either before or, sometimes, after conducting the study of primary interest
Pilot studies
type of independent-groups experiment in which participants are randomly assigned to IV groups and are tested on the DV just once.
Posttest-only design
How do experiments provide supporting evidence for Covariance?
Covariance is indicated by a difference in group means.
levels of an independent variable
Conditions
when participants either get better at a task from practice or get worse at a task due to fatigue
Practice effects
an extra dependent variable that researchers can insert into an experiment to convince them that their experimental manipulation worked
Manipulation checks
participants are exposed to all levels of the IV at roughly the same time, and a single preference is the DV.
Concurrent-measures designs
the control group that is exposed to an inert treatment
Placebo group (placebo control group)