The Experimental Design Process for Science Projects

Science Experimental Design

The importance of experimental design in science is that helps students infer about causes or relationships, as opposed to simply describe what happened in a canned experiment.

As students learn to develop their own experimental design they must be able to answer the most important question of all regarding the design process.

Essentially, they are determining a driving question and creating a science experiment to help find an answer for the question. This includes identifying and answering questions that their design does not answer.

Experimental Design Process

Driving Question – students must learn to not ask questions that result in a simple yes or no answer.Experimental design questions must be cause and effect, along with being open-ended.

An example:

• What is the impact of acid rain on the growth rate of dandelions during spring?

Variables – once students have identified the driving question for an experiment, the next step in the design process is to identify variables.

These include:

• Independent Variable – is what is manipulated or the treatment in an experiment.
• Dependent Variable – is what is observed from the effects of manipulating the treatment in an experiment.
• Control Variables – are factors that remain constant throughout an experiment.
• Extraneous Variables – influence the relationship between the independent and dependent variables of an experiment, which the student has no control over. These are variables influence the outcome of an experiment and are undesirable because they add error to an experiment.

Hypothesis – the next step in the design process is developing a hypothesis to determine if the experimental design is testable; i.e., are the independent and dependent variables measurable.

Here is a hypothesis checklist:

• Is the hypothesis based on information contained in driving question?
• Does the hypothesis include the independent and dependent variable?
• Is the hypothesis worded so that it can be tested in the experiment?

Hypothesis examples are:

• Raising the temperature of a cup of water (temperature is the independent variable) will increase the amount of sugar that dissolves (the amount of sugar is the dependent variable).
• If a plant receives fertilizer (fertilizer is the independent variable), then it will grow to be bigger than a plant that does not receive fertilizer (plant size is the dependent variable).

Impact of Using the Experimental Design Process

Now students can make a personal connection to scientific investigation process. A personal connection is essential to internalizing new knowledge and ways of learning. The key attributes of  students gain from this process is:

• learning how to design research
• learning how to ask questions
• internalizing new knowledge
• realizing that findings depend on experimental design
• increasing their level of understanding of science
• learning how to investigate like scientists

Additional Resources

Understanding Scientific Inquiry

Experimental Design