Experiment Design

Hypothesis An explanation of one or more phenomena that can be tested by observations, experiments, or both.

Parts of an Experiment 1. Hypothesis 3. Dependent Variable 2. Independent Variable 4. Controlled Variables 5. Control

Experiment A good testable question will often take the form of “How does ____ affect____?” It will focus your testing to only one factor (Example: “How does the amount of sunlight affect the growth of plants?” instead of “What affects the growth of plants?”).

Variables The above question includes the cause (the amount of sunlight) and the effect (the growth of plants), these are called variables.

Independent Variable The independent variable is the one variable you choose to change.

Dependent Variable The dependant variable changes in response to the change in the independent variable.

Scientific Hypothesis a suggested answer of how one variable affects the other. The hypothesis should describe the relationship between the independent and dependent variables. Often it follows an if-then pattern: If the amount of sun light is increased, then the plant will grow larger.

Controlled Variables To conduct a fair test we must ensure that other factors that may affect the outcome of the experiment are controlled or kept the same. These variables that are not changed are called controlled variables.

Control A sample that is left alone so that the tested samples may be compared to it. It helps scientists to ensure that unaccounted variables are not impacting the experiment. Not all experiments have a control

Examples A Skier wants to test which of three waxes he should use Dependent? Independent? Controlled Variables? Control?

A drug company wants to find out the effectiveness of a new drug. Independent Variable? Dependent Variable? Controlled Variables? Control?