Strengths and limitations of experimental research

Strengths

A properly designed and executed experiment is the most effective way of testing for the effects of one variable upon another. Two powerful strengths of this method of research are:

1. Conditions other than the experimental variable that could affect the dependent variable are minimized, if not eliminated completely; and
2. The experimental variable can be manipulated or controlled by the experimenter.

Together, these conditions allow rigorous testing of causal hypotheses. These are hypotheses stating a cause and effect relationship. Experimental research also has other positive features.   Many laboratory experiments are brief, inexpensive, require little special equipment, and can be easily carried out by one person.   Laboratory-based experiments also can be easily replicated, which allows for the accumulation of knowledge. Experiments can also be used to test the practical value of a new program, such as teaching techniques of family planning or for improving knowledge of nutrition.

Limitations

One of the main limitations of the experimental method is the difficulty of meeting the requirements for both internal and external validity.   Carefully controlled experiments, which are often high in terms of internal validity, frequently have low external validity, while quasi- experiments conducted in natural settings can be high on external validity, but often lack internal validity. In addition, experiments generally are not designed to provide empirical generalizations to a larger population.   Experimental and control groups generally are not randomly selected from a population: Hence, anything learned about these subjects cannot be used to describe parameters for any population. The small size of experimental and control groups also limits generalizing from the experimental results.   Finally, experiments in natural settings can be time consuming, require considerable coordination, and can be costly.

Aids

Internet resources

There is a large body of information on the Web about the design and conduct of experiments and quasi-experiments. Throughout this chapter, we have cited a few sites. Far more information can be found by entering "experimental design" or "quasi-experimental design" or some variation of these words in any search engine such as http://www.google.com or http://www.yahoo.com.