Experimental Design AP BIO

AP BIO UNIT 0

Null Hypothesis

States that there is no relationship between 2 variables: “The IDV will have no effect on the DV”

Example: The amount of sunlight does not affect plant growth.

Hypothesis

States that there is a relationship between 2 variables; findings probably did NOT occur due to chance events. Basically states that the IDV has an effect on the DV and predicts how changes in the IDV may influence the DV.

Example: Increasing sunlight exposure will lead to taller plants.

Positive Control Group

An experimental control that gives a positive result at the end of an experiment! (Positive Result: Dependent Variable Produced)

Positive controls are used to ensure that the experimental setup is capable of producing a positive outcome, therefore validating the experimental conditions.

Example: Peas exposed to a pH solution of 7 (neutral) respire.

Negative Control Group

An experimental control that does not give a response to the test. (Negative result: Dependent variable is NOT produced).

Negative controls help to ensure that any observed results are due to the independent variable and not other factors.

Example: Plastic beads exposed to pH solution of 7 (neutral) do not respire.