Skim Text 4B “Experimentation as a Scientific Research Method” and try to understand what it is about. Give a brief overview of its structure and contents.

Text 4B. EXPERIMENTATION AS A SCIENTIFIC RESEARCH METHOD

Experimentation is one scientific research method, perhaps the most recognizable, in a spectrum of methods that also includes de­scription, comparison, and modelling. While all of these methods share in common a scientific approach, experimentation is unique in that it involves the conscious manipulation of certain aspects of a real system and the observation of the effects of that manipulation. You could solve a cell phone reception problem by walking around a neighbourhood until you see a cell phone tower, observing other cell phone users to see where those people who get the best reception are standing, or looking on the web for a map of cell phone signal cover­age. All of these methods could also provide answers, but by moving around and testing reception yourself, you are experimenting.

In the experimental method, a condition or a parameter, gener­ally referred to as a variable, is consciously manipulated (often re­ferred to as a treatment) and the outcome or effect of that manipula­tion is observed on other variables. Variables are given different names depending on whether they are the ones manipulated or the ones observed: independent variable refers to a condition within an experiment that is manipulated by the scientist; dependent variable refers to an event or outcome of an experiment that might be affected by the manipulation of the independent variable. Scientific experi­mentation helps to determine the nature of the relationship between independent and dependent variables. While it is often difficult, or sometimes impossible, to manipulate a single variable in an experi­ment, scientists often work to minimize the number of variables be­ing manipulated. For example, as we move from one location to an­other to get better cell reception, we likely change the orientation of our body, perhaps from south-facing to east-facing, or we hold the cell phone at a different angle. Which variable affected reception: location, orientation, or angle of the phone? It is critical that scien­tists understand which aspects of their experiment they are manipu­lating so that they can accurately determine the impacts of that ma­nipulation. In order to constrain the possible outcomes of an experi­mental procedure, most scientific experiments use a system of con­trols.

In a controlled study, a scientist essentially runs two (or more) parallel and simultaneous experiments: a treatment group, in which the effect of an experimental manipulation is observed on a depen­dent variable, and a control group, which uses all of the same condi­tions as the first with the exception of the actual treatment. Controls can fall into one of two groups: negative controls and positive con­trols. In a negative control, the control group is exposed to all of the experimental conditions except for the actual treatment. The need to match all experimental conditions exactly is so great that, for exam­ple, in a trial for a new drug, the negative control group will be given a pill or liquid that looks exactly like the drug, except that it will not contain the drug itself, a control often referred to as a placebo. Nega­tive controls allow scientists to measure the natural variability of the dependent variable(s), provide a means of measuring error in the ex­periment, and also provide a baseline to measure against the experi­mental treatment.

Some experimental designs also make use of positive controls. A positive control is run as a parallel experiment and involves the use of an alternative treatment that the researcher knows will have an effect on the dependent variable. For example, when testing the ef­fectiveness of a new drug for pain relief, a scientist might administer treatment placebo to one group of patients as a negative control, and a known treatment like aspirin to a separate group of individuals as a positive control since the pain-relieving aspects of aspirin are well documented. In both cases, the controls allow scientists to quantify background variability and reject alternative hypotheses that might otherwise explain the effect of the treatment on the dependent vari­able.

Experiments are used across all scientific disciplines to investi­gate a multitude of questions. In some cases, scientific experiments are used for exploratory purposes in which the scientist does not know what the dependent variable is. In this type of experiment, the scientist will manipulate an independent variable and observe what the effect of the manipulation is in order to identify a dependent vari­able (or variables). Exploratory experiments are sometimes used in nutritional biology when scientists probe the function and purpose of dietary nutrients. In one approach, a scientist will expose one group of animals to a normal diet, and a second group to a similar diet ex­cept that it is lacking a specific vitamin or nutrient. The researcher will then observe the two groups to see what specific physiological changes or medical problems arise in the group lacking the nutrient being studied [Carpi, Egger, 2008].