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- Re-arrange the data in increasing order.
- If there are n data points, calculate (n+1)/4.
- Find the data point in position (n+1)/4, using interpolation if required. This is the LOWER QUARTILE.
- Find the data point in position 3*(n+1)/4, using interpolation if required. This is the UPPER QUARTILE.
In n is large (>30, say), don't bother to add 1: just work with the observations in the n/4th and 3n/4th positions.
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Continue Learning about Statistics
Calculating quartile deviation for grouped and ungrouped data?
(q3-q1)/2
What is the purpose of quartile deviation?
In a data sample, the purpose of quartile deviation is a way to measure data dispersion instead of using the range. The quartile deviation is found by subtracting the lower quartile from the upper quartile, and dividing this result by two.
The first quartile of a data set is 32 and the third quartile is 52. Which of these values in the data set is an outlier?
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The first quartile of a data set is 72 and the third quartile is 92. Which of these values in the data set is an outlier?
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The first quartile of a data set is 52 and the third quartile is 72. Which of these values in the data set is an outlier?
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