What makes a good experimental design?

Dependent Variable The variable that does not change with experimental conditions. Represents the parameter that is set before the experiment begins. For example, the dependent variables in our class experiment with body measurements was gender (male or female).

Independent Variable The variable that does change with experimental conditions. represents an experimental parameter that is not known before the experiment begins. For example, the independent variable in our class experiment with body measurements was height.

Control An experimental group that best represents the “normal” situation or the situation that would occur naturally. Not all experimental designs require the use of a control. Experiments not requiring a control normally consist of a number of treatment groups that are being compared. For example, finding the best product from a group of products.

Constants Environmental factors that do not change in the experiment. Devices or instruments that do not change in the experiment. Procedures that do not change in the experiment. Keeping the same people performing the experiments.

Number of Experimental Trials The higher the number of experimental trials the more dependable are the results. While the highest number of experimental trials are the most optimal, the more realistic number of experimental trials depend on factors such as cost of the experiment, the ease of doing the experiment, and how much time is allowed for the experiment.

Number of Samples Usually, the more the number of samples the more reliable the data for the experiment. The number of samples used for the experiment is affected by several factors including cost, time for experimentation, and complexity of the experiment. If there is to be a low amount of experimental trials, then the number of samples should be increased.

Timing and Sequence in the Experiment For certain types of experiments, the time when the experiment is done is very critical. Sometimes the sequence of experimental steps must be critically evaluated for the order of steps and the time between steps. Prior knowledge about your experimental system can be very helpful to getting the proper timing and sequence.

Realistic and Applicable Experimental Design Does the experimental design follow realistic conditions in the real world? Is the experimental design applicable to a “real world” situation? Try to reduce exaggerated conditions in your experimental design. Establish conditions that could easily be used in any applications.