In science you will conduct many different types of investigations. There are three main types of investigations: descriptive, comparative, and experimental. In this resource we will focus on comparative and experimental investigations.

Comparative investigations involve collecting data on different organisms/objects/features, or collecting data under different conditions (e.g., times of year, temperatures, locations) to make a comparison. In comparative investigations scientists look for patterns or trends by comparing similarities and differences over time and under various circumstances. Identifying the boiling points of three different liquids and using a hand lens to observe the external anatomy of two different insects are examples of comparative investigations.

Experimental investigations involve a process in which a "fair test" is designed and variables are actively manipulated, controlled, and measured in an effort to gather evidence to support or refute a causal relationship. Experimental investigations have a control group which does not receive any treatment. For example, a student might conduct an investigation to answer the question "What is the effect of light color on plant growth?" In this experiment, the variable color of light is changed by the student. The student may compare red light to green light to natural light.

In experimental investigations it is important to keep all other variables constant. In the example above, it would not be a fair test if the plants under the green light received a different amount of water. The items in an experiment that are kept the same are identified as the controls. The chart below summarizes the similarities and differences in comparative and experimental investigations.

This chart compares all three types of investigations.

Let's see what you have learned about comparative and descriptive investigations. Read each question below and decide which type of investigation it would lead to.

Question	Comparative	Experimental
What is the effect of sugar on yeast?	Interactive popup. Assistance may be required. Check Your Answer	Interactive popup. Assistance may be required. Check Your Answer
What is the difference in temperature at locations A and B at 12:00 noon?	Interactive popup. Assistance may be required. Check Your Answer	Interactive popup. Assistance may be required. Check Your Answer
How does running affect heart rate?	Interactive popup. Assistance may be required. Check Your Answer	Interactive popup. Assistance may be required. Check Your Answer
How does temperature affect the growth of mold?	Interactive popup. Assistance may be required. Check Your Answer	Interactive popup. Assistance may be required. Check Your Answer
What are the similarities and differences among prokaryotes and eukaryotes?	Interactive popup. Assistance may be required. Check Your Answer	Interactive popup. Assistance may be required. Check Your Answer
How do the phases of the moon change throughout the month?	Interactive popup. Assistance may be required. Check Your Answer	Interactive popup. Assistance may be required. Check Your Answer