Identifying Variables

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Identifying Variables&Designing Investigations :

Identifying Variables&Designing Investigations

Slide 2:

Variables Variables are things that vary and change

Slide 3:

Variables In any experiment there are 2 variables: an independent (or input) variable a dependent (or outcome) variable Let’s look at each type….

Independent Variable :

Independent Variable Independent Variable – something that is changed by the scientist What is tested What is manipulated Example 1 You decide the weight to apply, so: Weight is the independent variable. Investigating how a weight affects the length of an elastic band.

Slide 5:

Independent (input) variable This is the thing that you decide to change. You decide the initial temperature, so: initial temperature is the independent variable. Example 2 Investigating how the rate of cooling of a beaker depends on the initial temperature.

Dependent Variable :

Dependent Variable Dependent Variable – something that might be affected by the change in the independent variable What is observed What is measured The data collected during the investigation

Slide 7:

Dependent (outcome) variable This is the variable that changes as a result.It is the variable that you measure. Example 1 You measure the resulting length of the elastic band, so: Length is the dependent variable. Investigating how a weight affects the length of an elastic band.

Slide 8:

Dependent (outcome) variable This is the variable that changes as a result.It is the variable that you measure. You measure the temperature every minute as it cools, so: temperature is the dependent variable. Example 2 Investigating how the rate of cooling of a beaker depends on the initial temperature.

Control :

Control Control – a part(s) of an experiment that are not changed Also called constants Allow for a “fair test”

Slide 10:

Control These are all the variables that must not change, to make sure it is a fair test. Example 1 You must use the same elastic band all the time, and the same scale etc,so it is a fair test. Investigating how a weight affects the length of an elastic band.

For Example: :

For Example:

Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle. :

Students of different ages were given the same jigsaw puzzle to put together. They were timed to see how long it took to finish the puzzle.

Identify the variables in this investigation. :

Identify the variables in this investigation.

What was the independent variable? :

What was the independent variable? Ages of the students Different ages were tested by the scientist

What was the dependent variable? :

What was the dependent variable? The time it to put the puzzle together The time was observed and measured by the scientist

What was the control? :

What was the control? Same puzzle All of the participants were tested with the same puzzle. It would not have been a fair test if some had an easy 30 piece puzzle and some had a harder 500 piece puzzle.