Descriptive Study Vs. Controlled Experiments
It's not just what you study but how you study -- so true in school as well as in scientific research. Scientists use descriptive studies and controlled experiments as two different tools to find details about certain aspects of life, whether it be the spread of diseases or how drugs affect the mind and body.
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Descriptive Study -- What it Does
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Researchers at Michigan State University compare a descriptive study to a newspaper article that reports the "five W's" about a subject, and also answers the "so what?" question. These studies are often referred to as hypothesis-finding rather than hypothesis-testing studies. For example, a descriptive study may reveal details about how a certain disease spreads among human populations, where it spreads, why it's resistant to specific treatments and when the disease is most prevalent.
Controlled Experiment -- What it Does
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With the findings from a descriptive study researchers have the right impetus and foundation to form hypotheses that they can test in controlled experiments. In these experiments, scientists test different variables to see the influence these variations have on a given outcome. For example, if there's a hypothesis that changing the ambient temperature (the variable) surrounding a virus will cause it to spread more easily, then scientists can test that variable. The experiment would include control groups, where each group is exposed to the same temperature, and then a variable group that's exposed to either a raised or lowered temperature.
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Descriptive Study -- What it Doesn't Do
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Because descriptive studies don't involve comparing different groups -- as do controlled experiments -- researchers cannot form conclusions about causation, such as what causes a particular disease. Doing so is called "overstepping the data" and easily leads to misinterpretations and faulty conclusions. Therefore, descriptive studies should be viewed as valuable for collecting specific information that can inspire more-rigorous studies in controlled experiments. But even though descriptive studies can't pinpoint causation, as in the case of a disease, they can be immediately helpful in preventing negative effects. For example, the study can inform others about disease-prevalent areas they should avoid.
Controlled Experiment -- What it Doesn't Do
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A single controlled experiment that tests one variable cannot, by itself, ascertain whether the tested hypothesis is right. Researchers must also apply statistical analysis to determine if the variable was, in fact, the determining factor or if the results were simply random. In other words, the researchers must test multiple times and get the same results based on the applied variable. If they do, then there's a solid basis for validating the hypothesis. Additionally, a controlled experiment is precisely limited in the data it can gather, and may not be as immediately useful as would a descriptive study.
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References
- Michigan State University; Descriptive Studies, What They Can and Cannot Do; David Grimes and Kenneth Schulz
- California Department of Public Health: What is a Descriptive Study?
- Life; The Science of Biology; David Sadava, et al.
- Children's Mercy Hospital and Clinics: What is a Descriptive Study
- Biology Online: Controlled Experiment
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