Descriptive Statistics - Methods

notes on descriptive statistics for methods

a2 psychology with aqa

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  • Created on: 29-06-12 13:19
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Descriptive Statistics
There are two types of descriptive statistics covered:
Measures of central tendency ­ mean/median/mode
o Gives a typical value for the data set
o Tells you where the middle of the data set is
Measures of dispersion ­ range/standard deviation
o Indicates how the data are spread out
o Tells you what the rest of the data are doing
Advantage: it uses all the values in the set, so is most sensitive to variations in the data
Disadvantage: it can be artificially raised or lowered by an extreme value, or by skewed data
Use it when the data are normally distributed, unskewed and there are no outliers
Advantage: it is based on the order of the data, not their actual values, so not distorted by
extreme values
Disadvantage: however, this makes it less sensitive to variations in the data
Use it when you cannot use the mean because of skew, outliers etc
Advantage: it's the only measure suitable for summarising category/frequency data
Disadvantage: for many data sets there is no modal value, or there may be several
Use when dealing with frequency data, and/or where there is a clear modal value in the set


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