The essential feature of experimental research is that investigators deliberately control and manipulate the conditions which determine the events in which they are interested. At its simplest, an experiment involves making a change in the value of one variable—called the independent variable—and observing the effect of that change on another variable—called the dependent variable. Imagine that we have been transported to a laboratory to investigate the properties of a new wonder-fertilizer that farmers could use on their cereal crops, let us say wheat (Morrison, 1993:44-5). The scientist would take the bag of wheat seed and randomly split it into two equal parts. One part would be grown under normal existing conditions—controlled and measured amounts of soil, warmth, water and light and no other factors. This would be called the control group. The other part would be grown under the same conditions—the same controlled and measured amounts of soil, warmth, water and light as the control group, but, additionally, the new wonder-fertilizer. Then, four months later, the two groups are examined and their growth measured. The control group has grown half a metre and each ear of wheat is in place but the seeds are small. The experimental group, by contrast, has grown half a metre as well but has significantly more seeds on each ear, the seeds are larger, fuller and more robust. The scientist concludes that, because both groups came into contact with nothing other than measured amounts of soil, warmth, water and light, then it could not have been anything else but the new wonder-fertilizer that caused the experimental group to flourish so well. The key factors in the experiment were:
If x, then y; if frustration, then aggression…the researcher uses some method to measure x and then observes y to see if concomitant variation occurs.
|• the random allocation of the whole bag of wheat into two matched groups (the control and the experimental group), involving the|