What Is a Lab Experiment?

Hypothesis

• A hypothesis is an educated guess about how a specific process or situation will change when subjected to different conditions. A scientist might hypothesize that pea plants will grow more slowly when they are watered less frequently or that a balloon filled with helium will lift more weight than a balloon filled with hydrogen. A clearly defined hypothesis suggests what might happen as a result of the experiment. The lab experiment is designed to test the hypothesis.

Method

• Every lab experiment has a method, a well-defined sequence of steps the scientist follows to create the controlled conditions that will test the specific result the hypothesis suggests will occur. It is critical to the scientific method that an experiment be replicable. This means the method used in the experiment should be clear and consistent enough that any scientist with the right equipment and expertise would be able to carry out the same experiment in the same way and get the same results.

Controlling Variables

• Since a lab experiment is built on the idea of finding the effects of a single change on something, it is important to eliminate any variables that could affect the process of the experiment in unpredictable, inconsistent or unknown ways. When designing the experiment, the scientist must carefully consider all factors that could affect the outcome and then design ways to exclude all but one. A scientist exploring the effects of low water on pea plant growth, for example, would ensure all the plants get the same amount of sunlight.

Results

• The results of a lab experiment help the scientist decide whether her original hypothesis was right or wrong. An experiment that disproves a hypothesis is just as successful as one that proves the hypothesis, since the point is to increase an understanding of how the world works. The best experiments have consistent results over multiple attempts and provide enough data points to indicate a clear pattern of causality. This helps scientists strengthen their theories and opens the way for further testing and refinement in new lab experiments.