Then you need to think about possible extraneous and confounding variables and consider how you might control them in your experiment. Research questionĪir temperature just above the soil surface Start by simply listing the independent and dependent variables. To translate your research question into an experimental hypothesis, you need to define the main variables and make predictions about how they are related. Specifically, you ask how increased air temperature near the soil surface affects the amount of carbon dioxide (CO2) respired from the soil.

Example question 2: Temperature and soil respirationYou want to know how temperature affects soil respiration. Specifically, you ask how the number of minutes a person uses their phone before sleep affects the number of hours they sleep.

We will work with two research question examples, one from health sciences and one from ecology: Example question 1: Phone use and sleepYou want to know how phone use before bedtime affects sleep patterns. You should begin with a specific research question. If if random assignment of participants to control and treatment groups is impossible, unethical, or highly difficult, consider an observational study instead. Plan how you will measure your dependent variableįor valid conclusions, you also need to select a representative sample and control any extraneous variables that might influence your results.Assign subjects to groups, either between-subjects or within-subjects.Design experimental treatments to manipulate your independent variable.Consider your variables and how they are related.There are five key steps in designing an experiment: A good experimental design requires a strong understanding of the system you are studying. You manipulate one or more independent variables and measure their effect on one or more dependent variables.Įxperimental design means creating a set of procedures to systematically test a hypothesis. Guide to Experimental Design | Overview, 5 steps & ExamplesĮxperiments are used to study causal relationships.

Scientific experiments variables