2. How Science works: Types of Variables

3. Revision of variables Can you remember what is meant by… …an independent variable? …a dependent variable? …a control variable?

4. Revision of variables Summary: The independent variable is the one that you change or select. The dependent variable is the one changes as a result, and that you measure. The control variables must not change, so that it is a fair test.

5. Types of variables There are 4 other types of variables that you may meet. Their names are: Categoric Ordered Discrete Continuous We’ll look at two examples of each one.

6. Categoric variables These have word labels. Example 1 copper, iron, glass In this experiment on conduction of heat: The Categoric variables are:

7. These have word labels. Example 2 copper wire, iron wire, steel wire, etc In this experiment to find the resistance of wires: Categoric variables The Categoric variables could be:

8. Ordered variables These are categoric variables that can be ranked, in an order. Example 1 thick copper wire, thinner copper wire, very thin copper wire. In this experiment to find the resistance of wires: The Ordered variables could be:

9. These are categoric variables that can be ranked, in an order. Example 2 large parachute, medium parachute, small parachute. In an experiment to investigate a falling parachute: Ordered variables The Ordered variables could be:

10. These variables can only have whole number values, 1, 2, 3,… Example 1 1 weight, 2 weights, 3 … In an experiment to investigate the stretching of a spring: Discrete variables The discrete variables are:

11. These variables can only have whole number values, 1, 2, 3,… Example 2 number of layers of insulation = 1 layer, 2 layers, 3 … In an experiment on the cooling of an insulated beaker: Discrete variables The discrete variables are:

12. These variables can have any numerical value. Example 1 length of the spring = 15.1 cm, 15.5 cm, 15.9 cm … In this experiment to investigate the stretching of a spring: Continuous variables The continuous variable is:

13. These variables can have any numerical value. Example 2 the temperature of the water = 70.6 o C, 68.4 o C, 66.2 o C … In this experiment to investigate the cooling of water: Continuous variables The continuous variable is:

14. In summary Categoric These have word labels. (Bar chart) Ordered These categoric variables can be ranked, in an order. (Bar chart) Discrete These can only have whole number values. (Bar chart) Continuous These can have any numerical value. (Line graph)