EXPERIMENTAL METHOD

Question 1

Experimental design

Answer 1

manipulate an independent variable and observe the effect on behavior, as assessed by the dependent variable.

Question 2

Experimental control

Answer 2

allows researchers to make the causal inference that the independent variable caused the observed changes in the dependent variable.

Question 3

What is control?

Answer 3

an essential ingredient of experiments; gained through manipulation, holding conditions constant, and balancing

Question 4

When confounding occurs what will happen?

Answer 4

observed covariation exists, and therefore, the experiment lacks internal validity.

Question 5

treatment may be considered successful if …?

Answer 5

subjects in the treatment group rated more favorably on outcome variables than control group subjects.

Question 6

What are treatments

Answer 6

is the unique feature of experimental research that sets this design apart from all other research methods.

Question 7

Treatment manipulation helps

Answer 7

control for the “cause” in cause-effect relationships.

Question 8

What is a random selection

Answer 8

is the process of randomly drawing a sample from a population or a sampling frame.

Question 9

History threat

Answer 9

is the observed effects (dependent variables) are caused by extraneous or historical events rather than by the experimental treatment.

Question 10

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?

Answer 10

History threat

Question 11

Maturation threat

Answer 11

is the possibility that observed effects are caused by natural maturation of subjects rather than the experimental treatment.

Question 12

A general improvement in their intellectual ability to understand complex concepts are best example of?

Answer 12

Maturation threat

Question 13

Testing threat

Answer 13

is a threat in pre-post designs where subjects’ posttest responses are conditioned by their pretest responses

Question 14

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?

Answer 14

Testing threat

Question 15

Instrumentation threat

Answer 15

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

Question 16

Mortality threat

Answer 16

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

Question 17

Regression threat

Answer 17

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.

Question 18

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?

Answer 18

Regression threat

Question 19

Randomized Subjects, Pre test only

Answer 19

 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.

Question 20

Two essential elements Randomized Subjects, Pre test only

Answer 20

necessary for maximum control of the threats to internal validity: randomization and a control group.

Question 21

Advatanges of Randomized Subjects, Pre test only

Answer 21

1. Randomization, ensures statistical equivalence of the groups before introduction of the independent variable of pretest and X
2. Recommended for research on changing attitudes.
3. 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
4. It can be extended to include more than two groups if necessary.

Question 22

Disdvatanges of Randomized Subjects, Pre test only

Answer 22

1. Threats to internal validity are subject effects and experimenter effects
2. Does not permit the investigator to assess change
3. Difficult to perform
4. Costly

Question 23

Randomized Matched Subjects

Answer 23

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.

Question 24

Advatages Randomized Matched Subjects

Answer 24

1. useful in studies in which small samples
2. serves to reduce the extent to which experimental differences can be accounted for by initial differences between the groups
3. It controls preexisting intersubject differences on variables highly related to the dependent variable that the experiment is designed to affect.
4. Random procedure used to assign the matched pairs to groups adds to the strength of this design.
5. can be used with more than two groups by creating matched sets and randomly assigning one member of each set to each group

Question 25

Disadvatages

Answer 25

1. Subject to the difficulties mentioned previously in connection with matching as a means of control.
2. matching of all potential subjects must complete, If one or more subjects were excluded because an appropriate match could not be found, this would bias the sample

Question 26

Randomized Subjects, Pre test and post test control group design

Answer 26

• One randomly assigns subjects to the experimental and control groups and administers a pretest on the dependent variable.
• The treatment is introduced only to the experimental subjects (unless two different treatments are being compared), after which the two groups are measured on the dependent variable.

Question 27

Advantages of Randomized Subjects, Pre test and post test control group design

Answer 27

 ensures statistical equivalence between the groups prior to experimentation; also, the fact that the experimenter has control of the pretest can provide an additional check on the equality of the two groups on the pretest
 Controls most of the extraneous variables that pose a threat to internal validity. For example, the effects of history and maturation are experienced in both groups; therefore, any difference between the groups on the posttest measure could probably not be attributed to these factors.

Question 28

Disadvantages of Randomized Subjects, Pre test and post test control group design

Answer 28

Sanitizing effect:

Question 29

What is Sanitizing effect?

Answer 29

increased sensitivity to the study matter that caused them to change their response

Question 30

What is Solomon Three Group Design data?

Answer 30

The first two lines of this design are identical to randomized pre and post test design. However, the Solomon three-group design has the advantage of employing a second control group that is not pretested but is exposed to the treatment. This group, despite receiving the experimental treatment, is functioning as a control and is thus labeled control group.

Question 31

How can we analyze the Solomon Four Group Design data?

Answer 31

• The comparison between the posttest results of groups C and D, marked by line ‘D’, allows the researcher to determine if the actual act of pretesting influenced the results. If the difference between the posttest results of Groups C and D is different from the Groups A and B difference, then the researcher can assume that the pretest has had some effect upon the results
• The comparison between the Group B pretest and the Group D posttest allows the researcher to establish if any external factors have caused a temporal distortion. For example, it shows if anything else could have caused the results shown and is a check upon causality.
• The Comparison between Group A posttest and the Group C posttest allows the researcher to determine the effect that the pretest has had upon the treatment. If the posttest results for these two groups differ, then the pretest has had some effect upon the treatment and the experiment is flawed.
• The comparison between the Group B posttest and the Group D posttest shows whether the pretest itself has affected behavior, independently of the treatment. If the results are significantly different, then the act of pretesting has influenced the overall results and is in need of refinement.

Question 32

What is Quasi- Experimental Designs?

Answer 32

• Quasi-experimental designs are similar to randomized experimental designs in that they involve manipulation of an independent variable but differ in that subjects are not randomly assigned to treatment groups.
• Because the quasi-experimental design does not provide full control, it is extremely important that researchers be aware of the threats to both internal and external validity and considers these factors in their interpretation.
• Quasi- experimental designs are considered worthwhile because they permit researchers to reach reasonable conclusions even though full control is not possible.