Teacher’s Notes This sequence of slides is designed to introduce, and explain, the different types of variables (categoric, ordered, discrete, continuous), as explained on pages 360 in New Physics for You, 2006 edition. It should be used after the other PowerPoint on ‘Variables’. On each slide the key points are revealed step by step, at the click of your mouse (or the press of a key such as the space-bar). Before making the next mouse-click you can ask questions of the class or make statements about what is about to be revealed. This should help students to become clearer about the ideas involved. Naturally it pays to have quick practice-run first. To start the slide-show, press function-key F5 (or right-click->Full Screen) (to return to ‘normal view’ press the <Esc> key). For more free PowerPoint presentations, visit www.physics4u.co.uk

New Physics for You, page 360 How Science works: Types of Variables New Physics for You, page 360

About different types of variables, Learning Objectives You should learn : About different types of variables, How to identify them when doing your practical work.

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

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.

Categoric Ordered Discrete Continuous 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.

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

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

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

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

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

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

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

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

In summary Categoric These have word labels. Ordered These categoric variables can be ranked, in an order. Discrete These can only have whole number values. Continuous These can have any numerical value.

Understand the difference between - Categoric, - Ordered, Learning Outcomes You should now: Understand the difference between - Categoric, - Ordered, - Discrete, and - Continuous variables Be able to identify these variables when doing your practical work.

For more details, see: New Physics for You, page 360 For more free PowerPoints, visit the web-site at www.physics4u.co.uk

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