EXPERIMENTAL METHOD Flashcards
Please read and answer the question in your notebook or scratch paper.
Experimental design
manipulate an independent variable and observe the effect on behavior, as assessed by the dependent variable.
Experimental control
allows researchers to make the causal inference that the independent variable caused the observed changes in the dependent variable.
What is control?
an essential ingredient of experiments; gained through manipulation, holding conditions constant, and balancing
When confounding occurs what will happen?
observed covariation exists, and therefore, the experiment lacks internal validity.
treatment may be considered successful if …?
subjects in the treatment group rated more favorably on outcome variables than control group subjects.
What are treatments
is the unique feature of experimental research that sets this design apart from all other research methods.
Treatment manipulation helps
control for the “cause” in cause-effect relationships.
What is a random selection
is the process of randomly drawing a sample from a population or a sampling frame.
History threat
is the observed effects (dependent variables) are caused by extraneous or historical events rather than by the experimental treatment.
Students’ post-remedial math score improvement may have been caused by their preparation for a math exam at their school, rather than the remedial math program. This scenario is an example of?
History threat
Maturation threat
is the possibility that observed effects are caused by natural maturation of subjects rather than the experimental treatment.
A general improvement in their intellectual ability to understand complex concepts are best example of?
Maturation threat
Testing threat
is a threat in pre-post designs where subjects’ posttest responses are conditioned by their pretest responses
If students remember their answers from the pretest evaluation, they may tend to repeat them in the posttest exam. Not conducting a pretest can help avoid this threat. This scenario is an example of?
Testing threat
Instrumentation threat
which also occurs in pre-post designs, refers to the possibility that the difference between pretest and posttest scores is not due to the remedial math program
Mortality threat
refers to the possibility that subjects may be dropping out of the study at differential rates between the treatment and control groups due to a systematic reason, such that the dropouts were mostly students who scored low on the pretest
Regression threat
refers to the statistical tendency of a group’s overall performance on a measure during a posttest to regress toward the mean of that measure rather than in the anticipated direction.
If subjects scored high on a pretest, they will have a tendency to score lower on the posttest (closer to the mean) because their high scores (away from the mean) during the pretest was possibly a statistical aberration. This problem tends to be more prevalent in nonrandom samples and when the two measures are imperfectly correlated. This scenario is an example of?
Regression threat
Randomized Subjects, Pre test only
The designs in this category are called true experiments because subjects are randomly assigned to groups. Because of the control they provide, they are the most highly recommended designs for experimentation in education.
Two essential elements Randomized Subjects, Pre test only
necessary for maximum control of the threats to internal validity: randomization and a control group.
Advatanges of Randomized Subjects, Pre test only
- Randomization, ensures statistical equivalence of the groups before introduction of the independent variable of pretest and X
- Recommended for research on changing attitudes.
- useful in studies in which a pretest is either not available or not appropriate, such as in studies with kindergarten or primary grades, where it is impossible to administer a pretest because the learning is not yet manifest
- It can be extended to include more than two groups if necessary.
Disdvatanges of Randomized Subjects, Pre test only
- Threats to internal validity are subject effects and experimenter effects
- Does not permit the investigator to assess change
- Difficult to perform
- Costly
Randomized Matched Subjects
uses a matching technique to form equivalent groups. Subjects are matched on one or more variables that can be measured conveniently, such as IQ or reading score.
Advatages Randomized Matched Subjects
- useful in studies in which small samples
- serves to reduce the extent to which experimental differences can be accounted for by initial differences between the groups
- It controls preexisting intersubject differences on variables highly related to the dependent variable that the experiment is designed to affect.
- Random procedure used to assign the matched pairs to groups adds to the strength of this design.
- can be used with more than two groups by creating matched sets and randomly assigning one member of each set to each group