# Research Methods

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## Probability and Significance

• Probability is expressed a number between 0 and 1
• 0 means an event will not happen
• 1 means that an event will definitely happen
• P value will always be between 0 and 1
• Probability = number of particular outcomes / number of possible outcomes
• A significant result is one where there is a low probability that chance factors were responsible for any observed difference, correlation or association in the variales tested
• Psychologists have concluded that for most purposes, 5% level of significance will be used
• p = 0.05
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## Hypotheses

One tailed (directional) hypothesis:

Predicts the direction in whihc the change will take place when the IV is manipulated

Two tailed (non-directional) hypothesis:

It says that a change will take place when the IV is manipulated but does not indicate in which direction

Null hypothesis:

It predicts that no chance will take place and any change occuring is due to chance

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## Levels of Measurement

Nominal data:

Used when categorising something; named categories are established by the researcher and an item is counted when it falls into a particular category

Ordinal data:

Used when data is ranked so that it is possible to see the order of scores in relation to one another

Interval data:

Gives the rank order of scores but also details the precuse intervals between scores in precise units

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## Statistical Tests

Spearman's Rho:

• Used to test a correlation
• The data is ordinal, interval or ratio

Mann-Whitney:

• Testing for a difference
• Independant groups design

Wilcoxon:

• Testing for a difference
• Repeated measures design
• Ordinal data

Chi-Squared:

• Nominal data
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## Errors

Type One Error:

• Rejecting the null hypothesis when we should not
• P level too lenient
• Says there is a signififcant result when there is not

Type Two Error:

• Accepting a null hypothesis when we should
• P level too stringend
• Says there is no significant result when there is
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## Central Tendencies and Dispersion

Central Tendency:

• Mean (add up and divide by number of results)
• Median (put into order and find the middle value)
• Mode (most popular result)

Measure of Dispersion:

• Range (difference between highest and lowest result)
• Standard deviation (the spread of values around the mean)
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