Types of Data and Statistical Tests

Definitions of types of data in unit 4 Psychology research methods and the types of statistical tests that go with them.

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Types of Data

Nominal data ------> The level of measurement where scores are placed in categories.

i.e. smokers and non-smokers, pink and not pink etc.

Ordinal data------> The level of measurement where scores are ranked/ordered but no measurements are made.

i.e. Heights- smallest to largest etc.

Interval data-------> The levels of measurement where scores are ranked but the "distance between one score and another is known.

This "distance" is known as an interval.

i.e. Exact height measurements

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Types of Statistical tests

There are 4 statistical tests:

• Spearman's Rho
• Chi^2 (Chi square test)
• Wilcoxon Sign test
• Mann-Whitney test

Each test goes with a certain type of data and has a criteria which tells us when to use it.

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Data---------> Test

Interval data:

• Spearman's Rho
• Mann Whitney test

Ordinal data:

• Spearman's Rho
• Wilcoxon Sign test
• Mann Whitney test

Nomial data:

• Chi square test
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Chi Square test

Use when:

• The hypothesis predicts an association between two variables
• The sets of data are independant
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Spearman's Rho

Use when:

• The hypothesis predicts a correlation between two variables
• The two sets of data are pairs of scores from one person/thing
• The data are ordinal or interval
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Mann Whitney test

Use when:

• The hypothesis predicts a difference between two sets of data
• The two sets of data are from seperate groups of participants
• The data are ordinal or interval
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Wilcoxon Sign test

Use when:

• The hypothesis predicts a difference between two sets of data
• The two sets of data are pairs of scores from one person
• The data are ordinal or interval
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