The Three Types of Investigations:

DescriptiveComparativeExperimental

Descriptive Investigation

Describing and/or quantifyingparts of a system

DescriptiveInvestigations

• Involves describing and/or quantifying (counting) parts of a natural or man-made system.

Descriptive Investigations• An investigation used to explore questions in environmental

conditions you cannot control.– Ex. Jane Goodall’s study of chimpanzees.– Picture hyperlinked to: www.janegoodall.org/media/videos

A hypothesis is not required in these investigations.

Comparative Investigation

Collecting data on different organisms, objects, or features, or collecting data under different conditions

(e.g., times of year or locations) to make a comparison

ComparativeInvestigations

• Involves collecting data on different organisms, features or collecting data under different conditions (For example, times of year, temperatures, locations)

Comparative Investigations• Involves collecting data on different

organisms/objects/features, or collecting data under different conditions to make a comparison.

• Example: times of year, temperatures, locations

• Hypothesis: Pecan trees produce more pecans during the rainy season than they do during a drought.

ExperimentalInvestigations

• Involves designing a fair test in which variables are actively manipulated, controlled and measured in an effort to gather evidence to support or not support a hypothesis.

Experimental Investigation

A fair test in which variables are manipulated, controlled, and measured to gather evidence to support or

not support a hypothesis

Does the amount of fertilizer effect plant growth?

Research Question: Does the amount of fertilizer effect plant growth

Hypothesis Ex: The more fertilizer a plant receives the faster it will grow.

Gathering Data: Controlled experiment with one independent variable.

• Variables – When doing a science experiment, there are things that you, as the scientist, control to make sure your test results are dependable

• Constants – are the things that stay the same in an experiment.

• Control – is the trial/part/ thing that the other trail

are compared to. The control in an experiment on how fertilizer effects plant growth would be the plant without fertilizer. If in doubt, the control is usually the first trial in the experiment.

Terms Used in Investigations

Independent Variable or Manipulated Variable – The independent variable is the thing that you change in the experiment. All the other things in your experiment should stay the same. For example, in an experiment on how the amount of fertilizer effects the growth of plants, the independent variable is the type of fertilizer. We’ll use the same kind of pot, soil, and plant. We’ll have the plants get the same amount of light and stay in the same room at the same temperature. We’ll add the same amount of water. The only thing that will change is the kind of fertilizer.

Dependent Variable or Responding Variable – The dependent variable is the thing that changes because of the independent variable. For us, that would be the height of the plant. The height of the plant changed because we changed the type of fertilizer.