Essay Quasi-Experimental Design
You know that you seek a room marked with the numbers 1-0-1-2, so you press the button marked "10." The halves slide shut and enclose you within the cubicle, which jolts upward. A ride in an elevator may not seem like an experiment, but it, and each step taken towards its ultimate outcome, are common examples of a search for a causal relationship-which is what experimentation is all about.
Groups can be created in two ways: matching and randomization.In this example, even though the designers of the experiment have tried to remove all extraneous variables, results may appear merely coincidental.Since the goal of the experiment is to prove a causal relationship in which a single variable is responsible for the effect produced, the experiment would produce stronger proof if the results were replicated in larger treatment and control groups.In the example used in this guide (you'll find the example below), we discuss an experiment that focuses on three groups of plants -- one that is treated with a fertilizer named Mega Gro, another group treated with a fertilizer named Plant!, and yet another that is not treated with fetilizer (this latter group serves as a "control" group).On the other hand, you might find that although you turn the knob a great deal, sound doesn't increase dramatically.Or, you might find that turning the knob just a little adds more sound than expected.As such, researchers often have an idea, or hypothesis, about what effect will occur when they cause something.Few experiments are performed where there is no idea of what will happen.Thus far, we have explained that for experimental research we need: But what if we don't have all of those? Not a true experiment in the strictest scientific sense of the term, but we can have a quasi-experiment, an attempt to uncover a causal relationship, even though the researcher cannot control all the factors that might affect the outcome.A quasi-experimenter treats a given situation as an experiment even though it is not wholly by design.