Describe the attributes of an experimental research design. Then, decide whether

Question

Describe the attributes of an experimental research design. Then, decide whether each of the following topics could be studied using an experimental research design and then explain why or why not. a. Effect of parietal lobe damage on people’s ability to do basic arithmetic. b. Effect of being clinically depressed on the number of close friendships people have. c. Effect of group training on the social skills of teenagers with Asperger’s syndrome. d. Effect of paying people to take an IQ test on their performance on that test.

Explanation / Answer

EXPERIMENTAL RESEARCH AND DESIGN

Experimental Research - An attempt by the researcher to maintain control over all factors that may affect the result of an experiment. In doing this, the researcher attempts to determine or predict what may occur.

Experimental Design - A blueprint of the procedure that enables the researcher to test his hypothesis by reaching valid conclusions about relationships between independent and dependent variables. It refers to the conceptual framework within which the experiment is conducted.

Steps involved in conducting an experimental study

Identify and define the problem.

Formulate hypotheses and deduce their consequences.

Construct an experimental design that represents all the elements, conditions, and relations of the consequences.

1. Select sample of subjects.

2. Group or pair subjects.

3. Identify and control non experimental factors.

4. Select or construct, and validate instruments to measure outcomes.

5. Conduct pilot study.

6. Determine place, time, and duration of the experiment.

Conduct the experiment.

Compile raw data and reduce to usable form.

Apply an appropriate test of significance.

Essentials of Experimental Research

Manipulation of an independent variable.

An attempt is made to hold all other variables except the dependent variable constant - control.

Effect is observed of the manipulation of the independent variable on the dependent variable - observation.

Experimental control attempts to predict events that will occur in the experimental setting by neutralizing the effects of other factors.

Methods of Experimental Control

Physical Control

Gives all subjects equal exposure to the independent variable.
Controls non experimental variables that affect the dependent variable.

Selective Control - Manipulate indirectly by selecting in or out variables that cannot be controlled.

Statistical Control - Variables not conducive to physical or selective manipulation may be controlled by statistical techniques (example: covariance).

Validity of Experimental Design

Internal Validity asks did the experimental treatment make the difference in this specific instance rather than other extraneous variables?

External Validity asks to what populations, settings, treatment variables, and measurement variables can this observed effect be generalized?

Factors Jeopardizing Internal Validity

History - The events occurring between the first and second measurements in addition to the experimental variable which might affect the measurement.

Example: Researcher collects gross sales data before and after a 5 day 50% off sale. During the sale a hurricane occurs and results of the study may be affected because of the hurricane, not the sale.

Maturation - The process of maturing which takes place in the individual during the duration of the experiment which is not a result of specific events but of simply growing older, growing more tired, or similar changes.

Example: Subjects become tired after completing a training session, and their responses on the Posttest are affected.

Pre-testing - The effect created on the second measurement by having a measurement before the experiment.

Example: Subjects take a Pretest and think about some of the items. On the Posttest they change to answers they feel are more acceptable. Experimental group learns from the pretest.

Measuring Instruments - Changes in instruments, calibration of instruments, observers, or scorers may cause changes in the measurements.

Example: Interviewers are very careful with their first two or three interviews but on the 4th, 5th, 6th become fatigued and are less careful and make errors.

Statistical Regression - Groups are chosen because of extreme scores of measurements; those scores or measurements tend to move toward the mean with repeated measurements even without an experimental variable.

Example: Managers who are performing poorly are selected for training. Their average Posttest scores will be higher than their Pretest scores because of statistical regression, even if no training were given.

Differential Selection - Different individuals or groups would have different previous knowledge or ability which would affect the final measurement if not taken into account.

Example: A group of subjects who have viewed a TV program is compared with a group which has not. There is no way of knowing that the groups would have been equivalent since they were not randomly assigned to view the TV program.

Experimental Mortality - The loss of subjects from comparison groups could greatly affect the comparisons because of unique characteristics of those subjects. Groups to be compared need to be the same after as before the experiment.

Example: Over a 6 month experiment aimed to change accounting practices, 12 accountants drop out of the experimental group and none drop out of the control group. Not only is there differential loss in the two groups, but the 12 dropouts may be very different from those who remained in the experimental group.

Interaction of Factors, such as Selection Maturation, etc. - Combinations of these factors may interact especially in multiple group comparisons to produce erroneous measurements.

Factors Jeopardizing External Validity or Generalizability

Pre-Testing -Individuals who were pretested might be less or more sensitive to the experimental variable or might have "learned" from the pre-test making them unrepresentative of the population who had not been pre-tested.

Example: Prior to viewing a film on Environmental Effects of Chemical, a group of subjects is given a 60 item antichemical test. Taking the Pretest may increase the effect of the film. The film may not be effective for a nonpretested group.

Differential Selection - The selection of the subjects determines how the findings can be generalized. Subjects selected from a small group or one with particular characteristics would limit generalizability. Randomly chosen subjects from the entire population could be generalized to the entire population.

Example: Researcher, requesting permission to conduct experiment, is turned down by 11 corporations, but the 12th corporation grant permission. The 12th corporation is obviously different then the others because they accepted. Thus subjects in the 12th corporation may be more accepting or sensitive to the treatment.

Experimental Procedures - The experimental procedures and arrangements have a certain amount of effect on the subjects in the experimental settings. Generalization to persons not in the experimental setting may be precluded.

Example: Department heads realize they are being studied, try to guess what the experimenter wants and respond accordingly rather than respond to the treatment.

Multiple Treatment Interference - If the subjects are exposed to more than one treatment then the findings could only be generalized to individuals exposed to the same treatments in the same order of presentation.

Example: A group of CPA’s is given training in working with managers followed by training in working with comptrollers. Since training effects cannot be deleted, the first training will affect the second.

Tools of Experimental Design Used to Control Factors Jeopardizing Validity

Pre-Test - The pre-test, or measurement before the experiment begins, can aid control for differential selection by determining the presence or knowledge of the experimental variable before the experiment begins. It can aid control of experimental mortality because the subjects can be removed from the entire comparison by removing their pre-tests.

However, pre-tests cause problems by their effect on the second measurement and by causing generalizability problems to a population not pre-tested and those with no experimental arrangements.

Control Group -The use of a matched or similar group which is not exposed to the experimental variable can help reduce the effect of History, Maturation, Instrumentation, and Interaction of Factors. The control group is exposed to all conditions of the experiment except the experimental variable.

Randomization - Use of random selection procedures for subjects can aid in control of Statistical Regression, Differential Selection, and the Interaction of Factors. It greatly increases generalizability by helping make the groups representative of the populations.

Additional Groups - The effects of Pre-tests and Experimental Procedures can be partially controlled through the use of groups which were not pre-tested or exposed to experimental arrangements. They would have to be used in conjunction with other pre-tested groups or other factors jeopardizing validity would be present.

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