Understanding Experimental Design

Experimental Design

• Experimental design is a way to test a hypothesis through a series of steps to create controlled conditions for an experiment and limit exposure to outside interference.
• The purpose of experimental design is to form a conclusion based on a hypothesis, and the outcome can lead to supporting evidence of scientific law and scientific theory.

Independent and Dependent Variables

• Independent variable is manipulated in an experiment, and the experimenter causes it to change.
• Dependent variable changes as an effect of the independent variable being changed.

Scientific Law and Theory

• Scientific theory explains why things occur the way they do after significant repeated experiments.
• Scientific law is a pattern, typically established through an equation.
• A theory cannot become a law, and a law cannot become a theory.

Good Experiment

• A good experiment requires background knowledge in the area of the experiment.
• Proper equipment is necessary, and it must be accurate and precise.
• Accuracy is how close the values collected are to the real value, and precision is how close all measurements are to one another.

Experimental Design Process

• The experimental design process has five steps: define variables, formulate a hypothesis, design an experiment, assign subjects, and measure the dependent variable.
• The process starts with having a testable idea (hypothesis) and asking questions to decide on what information to find with the experiment.

Define Variables

• Defining variables is the first step in the experimental design process.
• There are three types of variables: independent, dependent, and control.
• Independent variable is what the experimenter will change, and the dependent variable changes due to the independent variable.

Formulate Hypotheses

• A hypothesis is an educated guess about what the outcome of the experiment will be before the experiment is conducted.
• The purpose of a hypothesis is to prove or disprove it at the end of the experiment.

Experimental Design Science (Treatment and Control Group)

• Experiments have a treatment group and a control group.
• The treatment group is the group that the experiment is performed on, and the control group does not receive any changes or treatment.

Assign Subjects

• Assigning subjects in an experiment could be a random selection, random assignment, or both.
• Random selection is picking a population for the experiment, and random assignment is how the subjects are grouped for the experimental design.

Measure the Dependent Variable

• The dependent variable is measured as part of the experiment, and the change of the dependent variable is the value needed to analyze the data.
• The results are measured by collecting qualitative or quantitative values.

Learn about the basics of experimental design, including independent and dependent variables, cause-and-effect relationships, and how to test a hypothesis.