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 & 2011 editions.

It should be used after the other PowerPoint on ‘Variables’.

Note : When you start this PowerPoint if you see a message about “Read-only embedded fonts” then you are recommended to select “Open Read-Only” as this (i) gives a clearer font for those at the back of the room and (ii) ensures that the text-highlighting of key words is correct.

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).

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How Science works:

Types ofTypes of

VariablesVariables

New Physics for You, page 360

• About different types of variables,

• How to identify them when doing your practical work.

Learning Objectives

You should learn :

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 variableis the one changes as a result, and that you measure.

The control variables must not change, so that it is a fair test.

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

copper, iron, glass

In this experiment on conduction of heat:

The Categoric variables are:

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:

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:

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:

These variables can only have whole number values, 1, 2, 3,…

Example 1

1 weight, 2 weights, 3 weights, …

In an experiment to investigate the stretching of a spring:

Discrete variables

The discrete variables are:

These variables can only have whole number values, 1, 2, 3,…

Example 2

number of layers of insulation = 1 layer, 2 layers, 3 layers, …

In an experiment on the cooling of an insulated beaker:

Discrete variables

The discrete variables are:

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:

These variables can have any numerical value.

Example 2

the temperature of the water = 70.6oC, 68.4oC, 66.2oC …

In this experiment to investigate the cooling of water:

Continuous variables

The continuous variable is:

In summary

• CategoricThese have word labels.

• OrderedThese categoric variables can be ranked,

in an order.

• DiscreteThese can only have whole number

values.

• ContinuousThese can have any numerical value.

• Understand the difference between- Categoric, - Ordered,- Discrete, and - Continuous variables

• Be able to identify these variables when doing your practical work.

Learning Outcomes

You should now:

For more details, see:

New Physics for You, page 360

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