Outliers
In this article we shall cover outliers in statistics
Summary
An outlier is any value which is;
-
greater than the upper quartile + 1.5 × interquartile range
or
less than the lower quartile – 1.5 × interquartile range
Finding Outliers
The blood glucose of 30 females is recorded. The results, in mmol/litre are shown in the stem and leaf diagram shown below;
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An outlier is an observation that falls either 1.5 × interquartile range above the upper quartile or 1.5 × interquartile range below the lower quartile
- Find the quartiles
- Find any outliers
-
Lower quartile
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So we pick the 8th term
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Upper quartile
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So we pick the 23rd term.
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Median
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So we pick the 15.5th term
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Outliers are values less than 3.3 – 1.5 × 0.8 = 2.1 and values greater than 4.1 + 1.5×0.8 = 5.3 therefore 5.6 is an outlier
