Types of Data in Psychology Experiments

Mar 30, 2008
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Levels of Data
by: David

When we carry out research sometimes we just count how often things occur, this is known as category data, also known as nominal or frequency data. Other times we record the order of things, this is known as ordinal data, also known as ranked data and sometimes we directly measure things using a variety of implements, rulers, clocks etc. and this is known as interval or ratio data.

The best way to understand these different types of data is to apply them to a simple example. Take height for instance.

Get a piece of paper and write down TALL on the left hand side of the page and SHORT on the right hand side of the page. Now, think about 6 people you know (family, friends etc) and considering their height, allocate (write their name) in either the Tall or the Short category.

This is an example of collecting category (nominal/frequency) data. All it does is record the frequency of occurrences of particular categories e.g. 4 Tall and 2 Short.

In order to get some more height information, you could ask your chosen family and friends to get in line with the tallest at the front and the shortest at the back. This would be an example of ordinal data and it gives you more information compared to category (nominal/frequency) data e.g. you know have information about relative position (person at the back is the smallest etc). But what it doesn't tell you about is relative difference, e.g. how much taller is the person at the front than the person at the back.

In order to get this level of information, you would need a tape measure to record each persons height in centimeters or inches. This would be an example of interval data.

So the thing to note here is that the amount of information contained within the level of data increases as you move from category, to ordinal, to interval.

If you are not sure what type of data you have, ask yourself have I simply noted frequency of occurrences (Category data)? Have I produced ordered (ranked) information (ordinal data)? Have I produced precisely measured information (interval data)?

Types of Data in Psychology Experiments

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