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- these are statistical measures that summarize the amount of spread or variation in the distribution of values in a variable.
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- the more similar the scores are to each other, the lower the measures of dispersion will be.
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- it describes how values are spread within the distribution
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- the less similar the scores are to each other, the higher the measures of dispersion will be.
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- it also describe how similar a set of scores are to each other.
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- in general, the more spread out a distribution is, the larger the measure of dispersion will be.
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- it is the difference between the largest and smallest number in a set of observation.
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- the range is rarely used in scientific work as it is fairly insensitive.
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- it is used mostly for quick and easy indication of variability.
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- the range can be used when you are presenting your results to people with little or no knowledge of statistics.
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- it can be used with ordinal or interval- ratio variables.
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- two diff sets of data may have same range.
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1, 1, 1, 1, 9 vs 1, 3, 5, 7, 9
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Ungroup data
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Group Data
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Range= Highest Score - Lowest Score
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Range= Highest Class Mark - Lowest Class Mark
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- it is defined as the difference of the first and third quartile of a data set.
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- it is a measure where the "middle fifty" lies in the data set.
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- therefore, because it uses the middle 50%, it is not affected by outliers or extreme values.
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Q3 = also known as UPPER QUARTILE
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Q1= also known as LOWER QUARTILE
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2 IMPORTANT MEASURES OF DISPERSION
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- variance
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- standard deviation
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