In Bio114, for your pleasure and edification, we have developed several computer simulations of laboratory exercises. To view these exercises you need the (free) Flash plug-in. If you do not see anything in the space below, you can download it here. You may have to close and restart your browser to complete the installation, just follow the instructions.

Controls and Variables

Experimental Methods and Controls - Improperly designed experiments often yield little information. A properly designed experiment has the following characteristics:

• It should have an independent variable (variable being changed by the experimenter.
• It should have a dependent variable (variable being observed that changes in response to the independent variable).
• It should have controlled variables (all the variables that will be the same in each experiment-not to be confused with the control).
• It should have controls (tests in which the independent variable is kept constant in order to measure changes in the dependent variable, or a reference decided on by the experimenter as a standard for comparison) .

Ther are several types of controls for experiments. Two types are listed below.

Positive Controls - see if an expected positive result will be observed. This is a good way to make sure all your solutions (or independent variables) are what they should be.

Negative Controls - see if an expected negative result will be observed

An Example Experiment . The IKI test - IKI is a solution that turns dark blue/black when put in contact with starch. This test is performed by adding a couple drops of the IKI solution to a small quantity of the sample to be tested. In general, the more starch present, the darker blue the color. The ? tube below contains an unknown solution.