Chapter 7

What are some ethical issues to consider with experiments?

- Deception - Selective Distribution of Benefits: how much researchers can influence the benefits subjects receive as part of the treatment.

Limitations to true experiment designs

- Do not help researchers identify the mechanisms by which treatments have their effects - Do not guarantee that the researcher has been able to maintain control over the conditions to which subjects are exposed after they are assigned to the experimental and comparison groups.

Experimental, comparison, and control groups

- Experimental Group: the group of subjects in an experiment that receives the treatment or experimental manipulation - Comparison Group: the group of subjects in an experiment that has been exposed to a different treatment (or value of the independent variable) than the experimental group - Control Group: a comparison group of subjects that receives no treatment.

Pretest & Posttest

- Posttest: The measurement of an outcome (dependent) variable after an experimental intervention or after a presumed independent variable has changed for some other reason - Pretest: Measurement of an outcome (dependent) variable prior to an experiemental intervention or change in a presumed independent variable for some other reason. (A true experiment does not require a pre test) -Exact same, just at a different time

Solomon four-group design

- Type of experimental design that combines a randomized pretest-posttest control group with a randomized posttest-only design, resulting in two experimental groups and two comparison groups. -Pretest to groups 1 and 2 -Stimulus to groups 1 and 3 -Posttest to all 4 groups -Most comprehensive true experiment

What are the weaknesses of the experimental method?

-Artificiality of laboratory setting. -Social processes that occur in a lab might not occur in a more natural social setting. -Experimenter effect -Lack of control -Sample size

What are the strengths of the experimental method?

-Establishing causality: isolation of the experimental variable over time. -Control -Longitudinal analysis -Replication: experiments can be replicated several times using different groups of subjects.

Static-group comparison

-Experimental and control groups -No pretests -Does not assume randomization of subjects -Best as a pre-experimental design

Posttest-only control group design

-Includes Groups 3 and 4 of the Solomon design -With proper randomization, only these groups are needed to control the problems of internal invalidity and the interaction between testing and stimulus.

What factors threaten external validity?

-Interaction effects -Hawthorne effect -Modeling effect -Problem with volunteer subjects

One-group pretest-posttest design

-No control group -Experimental group receives pretest, experimental stimulus, and posttest

One-shot case study

-No pretest -No control group -Only experimental group, experimental stimulus, and posttest

Causality in nonexperiments

-clear evidence of association between variables -longitudinal designs and some cross sectional designs allow for time order -nonspurious relationships are almost impossible -one-shot case studies facilitate investigation of contextual effects

Causality in true experiments

-unambiguous association between variables -time order if pretest is done -nonspurious relationships between variables due to randomization

Causality in quasi-experiments

-unambiguous association between variables -time order in before-and-after designs -context in which change occurs

Ex-post facto control group designs

A nonexperimental design in which comparison groups are selected after the treatment, program, or other variation in the independent variable has occurred

Hawthorne Effect

A phenomenon whereby individuals improve or modify an aspect of their behavior in response to their awareness of being observed.

Before-and-after design

A quasi-experimental design consisting of several before-after comparisons involving the same variables but no comparison group.

Nonequivalent control group design

A quasi-experimental design in which there are experimental and comparison groups that are designated before the treatment occurs, but they are not created by random assignment.

Quasi-experimental design

A research design in which there is a comparison group that is comparable to the experimental group in critical ways, but subjects are not randomly assigned to the comparison and experimental groups

Double-blind experiment

An experiment in which information about the test that might lead to a bias in the results is concealed from the tester AND the subject.