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Maths

Sampling - Higher

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There are a number of sampling methods such as random and stratified. You should try to make sure that the sample is representative.

Before working through this section, you should have already revised Questionnaires.

# Discrete and continuous measures

There are two types of variable - discrete and continuous.

A discrete variable can only take certain values from a finite set.

A continuous variable can take any value.

Example

The number of people in a car can only be a whole number: 1, 2, 3, 4...

It is not possible to have 31/2 or 21/4 people in a car, so the number of people in a car is a discrete variable.

The time taken to run 100 m can take any value, such as 41.35 seconds, 27.371 seconds, and so on.

Time is therefore a continuous variable.

Question

Is shoe size a discrete or continuous variable?

Shoe size is a discrete variable as it can only take certain values - eg, 4, 41/2, 5, 51/2, 6, etc.

In this example the values are not whole numbers but they still count as discrete because shoes only come in half sizes.

Question

Is the length of someone's foot a discrete or continuous variable?

The length of someone's foot is a continuous variable as it can take any value - eg, 17.9 cm, 22.452 cm, 25 cm, etc.

Question

Is the weight of cat a discrete or continuous variable?

The weight of a cat is a continuous variable as it can take any value - for example, 3 kg, 3.567 kg, 4.01 kg, etc.

Question

Is the number of stars a discrete or continuous variable?

The number of stars is a discrete variable because we can only have a whole number of stars. This is true even if we can't count them all.

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