Objectives:1. Students will be able to identify

and construct the different parts of an experiment.

Lesson Vocabulary

• Independent variable• Dependent variable• Levels of the independent

variable• Control• Repeated trials• Prediction (hypothesis),

What is an Experimentand

What is not an Experiment• An experiment can be a test of the effect

of different actions carried out by the experimenter

• A test comparing differing conditions as some action is carried out.

An Experiment is not

• An exercise to measure the density of a piece of metal.

• A survey of different types of plants or animals along a beach.

• An experiment starts and finishes with the factors that change during the experiment

• These factors are called variables.

Independent and Dependent Variable

• The independent variable is the one the experimenter purposely changes.

• The dependent variable changes in response to the purposeful change.

What is the independent and what is the dependent

Variable

There are many other factors that could be changed by the experimenter, and have an effect on the outcome of the experiment.

• Factors that could be changed but which are deliberately held constant are referred to as Constants.

Levels of the Independent Variable

• Often the independent variable that is manipulated by the experimenter will have several different values.

• Allows the testing of only one variable at a time.

• One of the levels of the independent variable will serve as a reference point or “normal” value of which the other levels will be compared to.

• This is the Control!

• Every experiment should be carried out several times and then the results of the individual trials averaged together.

• Makes for a more reliable test, and decreases the possibility of obtaining a misleading result.

So, How many trials should you do?

• The general rule is that students should repeat the experiment as many times as it is convenient and practical to do so.

Formally known as the Hypothesis

• Written in the form of a “if-then” statement.

• Linking the independent variable to the dependent variable.

• Based on the student’s past experiences as well as information they have been able to gather while carrying out background research.