Variables

Key components

• Independent Variable factor manipulated by the experimenter and identified in the research question and the hypothesis
• Dependent Variable is the factor that changes as a result of a change in the independent variable
• Fixed variable(s) are the factors that could affect the dependent variable so they are kept unchanged

This is often effectively shown in a table:

Sentence starters

❏ The independent variable is...

❏ The independent variable will be changed by increasing / decreasing from ... to ...

❏ The independent variable will be changed in increments of ...

❏ The dependent variable is...

❏ The dependent variable will be measured by...

❏ The measurements will be repeated ... times to be more reliable.

❏ ... will be controlled by ... because ...

Examples

Flying an airplane – initial height vs distance flown

Level 1-2:

Independent variable: distance (note this is wrong)

Dependent variable: height (note this is wrong)

Control variables: same way of throwing, same environment.

Level 3-4:

Independent variable: initial height

The paper airplane will be thrown from different initial heights.

Dependent variable: distance

The different distances the paper airplane travels will be measured.

Control variables:

The paper airplane will be thrown with the same force and same angle by releasing at the same place every time.

Level 5-6:

Independent variable: initial height (cm)

The paper airplane will be thrown from different initial heights. The heights will be 50 cm, 100 cm, 125 cm, 150 cm, 175 cm, 200 cm, 225 cm and 250 cm. There will be five trials for each height.

Dependent variable: distance (cm)

The different distances the paper airplane travels will be measured by measuring the distance from where the paper airplane is released to where the paper airplane lands.

Control variables:

The paper airplane will be thrown with the same force and same angle by releasing at the same place every time. The same environment will be used for all of the trials.

Level 7-8:

Independent variable: initial height (cm)

The paper airplane will be thrown from different initial heights. The heights will be 50 cm, 100 cm, 125 cm, 150 cm, 175 cm, 200 cm, 225 cm and 250 cm. There will be five trials for each height. The measurements of the different heights will be marked on the wall. For higher heights a desk will be used to throw the paper airplane (see risk assessment).

Dependent variable: distance (cm)

Tape will be placed on the ground directly below where the initially release of the paper airplane takes place. A mark will be set at the point where the paper airplane initially lands (not where it slides to). The distance from the tape to the mark will be measured using a tape measure.

Control variables:

The paper airplane will be thrown with the same force and same angle by releasing at the same place every time. A place on the paper airplane will be marked so the paper airplane is always thrown from the same point on the plane. The same classroom will be used for all of the trials, with all air conditioning units turned off and any other impacts kept to a minimum.