PSYC 2094 Chapters 9-10
Terms in this set (50)
modifications of the participant's physical or social environment
vary the independent variable through the verbal instructions that participants receive
create physical changes in the participant's body through surgery or the administration of drugs
a preliminary study that examines the usefulness of manipulations or measures that later will be used in an experiment
questions designed to determine whether the independent variable was manipulated successfully
Simple Random Assignment
participants are placed in conditions in such a way that every participant has an equal probability of being in any experimental condition
Matched Random Assignment
participants are first matched into homogenous blocks, and then participants within each block are assigned randomly to conditions
Repeated measures design
an experimental design in which each participant serves in all conditions of the experiment; also called a within-subjects design
occur when the effects of a particular experimental condition are contaminated by its order in the sequence of experimental conditions in which participants are tested.
participants' responses on the dependent variable are affected by the fact that they have completed the dependent variable many times
participants become tired or bored as the experiment progresses
participants gradually become suspicious of the hypothesis as the experiment progresses
effects of one treatment condition are still present when the participant is tested in another condition
involves presenting the levels of the independent variables in different orders to different participants
Is that part of the total variance in participants' responses that reflects differences among the experimental groups.
Is the portion of the systematic variance that is due to the independent variable
Is the portion of the systematic variance that is due to extraneous variables that differ systematically between the experimental groups. Confound variance must be eliminated.
Is the portion of the total variance in participants' responses that remains unaccounted for after systematic variance due to the independent variable is removed. It is variance that is unrelated to the independent variable(s) under investigation in an experiment.
is the degree to which a researcher draws accurate conclusions about the effects of the independent variable on a dependent variable.
Biased assignment of participants to conditions
effects are due to initially nonequivalent groups rather than to the independent variable; this can occur when random assignment fails
Participants drop out of experimental conditions at different rates, making the experimental groups no longer equivalent
Completing a pretest leads participants to react differently to the independent variable than they would have reacted had they not been pretested
extraneous events occurring outside of the research setting have an effect on participants' responses
Changes in participants' responses between pretest and posttest are due to the passage of time rather than to the independent variable (e.g., aging, fatigue, hunger)
Miscellaneous design confounds
Something other than the independent variable differs systematically between the experimental conditions
Experimenter expectancy effect
occurs when a researcher's expectations about the outcome of a study influences participants' reactions.
occur when aspects of a study indicate to participants how they should respond.
pre-existing differences between people; this is the most common source of error variance
at the time of the experiment, participants differ in how they feel (e.g., mood, health, fatigue, interest)
differences in the environment in which the study is conducted (e.g., noise, time of day, temperature)
despite their best efforts, experimenters do not always treat all participants exactly the same
unreliable measures increase error variance
Is the degree to which the results obtained in one study can be replicated or generalized to other samples, research settings, and procedures
One Way Experimental Design
one in which only one independent variable is manipulated.
Randomized Groups Design
participants are assigned randomly to one of two or more conditions
Matched Subjects Design
participants are matched into blocks on the basis of a relevant variable, then randomly assigned from blocks to one of two or more conditions
Repeated Measures Design
each participant serves in all experimental conditions
Posttest only design
dependent variable is measured only after the experimental manipulation of the independent variable
Pretest only design
dependent variable is measured twice, both before and after the experimental manipulation
Administering the pretest may lead participants to respond differently to the independent variable than they would had they not been pretested
An experimental design in which two or more independent variables are manipulated.
Randomized groups factorial design
Participants are assigned randomly to one of the possible combinations of the independent variables.
Matched groups factorial design
Participants are first matched into blocks on the basis of some variable that correlates with the dependent variable. The participants in each block are then randomly assigned to one of the experimental conditions.
Repeated measures factorial design
Each participant participates in every experimental condition
Mixed factorial design
Participants are randomly assigned to only one level of some independent variable(s), but receive every level of other independent variable(s); also called a between-within design
An independent variable is the effect of that independent variable while ignoring the effects of all other independent variables in the design
An interaction occurs when...
the effect of one independent variable differs across the levels of another independent variable.
participants scoring below the median on the subject variable are classified as low, and all participants scoring above the median are classified as high
Extreme groups procedure
select participants who score extremely high or low on a particular subject variable