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Like the standard deviation, the interquartile range (IQR) is a descriptive statistic used to summarize the extent of the spread of your data. The IQR is the distance between the 1st quartile (25th percentile) and 3rd quartile (75th percentile).
Q3 - Q1 = IQR
To find these numbers you must divide your data set in half, and find the median of each half and that will be your Q1 and Q3.
If you have an odd number, then EXCLUDE the median of the entire set, so as follows:
For example, take the following dataset:
3 5 7 8 9 21 40 90 120
We exclude the 9 as the median of the whole set and the 1st quartile is 6 (5+7 divided by 2) and the 3rd quartile is 65 (40+90 divided by 2), making the IQR = 65-6=59.
OR
If you have this set:
3 5 7 8 40 90 120
We exclude the 8 as the median of the whole set and the 1st quartile is 5 and the 3rd quartile is 90. (90 - 5 = 85.)
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Why is the interquartile range a more appropriate measure for spread than the range?
the interquartile range is not sensitive to outliers.
What is unaffected by outliers?
interquartile range
What does interquartile range mean?
The interquartile range is the upper quartile (75th percentile) minus (-) the lower percentile (75th percentile). The interquartile range uses 50% of the data. It is a measure of the "central tendency" just like the standard deviation. A small interquartile range means that most of the values lie close to each other.
How do you find the interquartile range in a set of data?
how do you find the interquartile range of this data
What includes the range and the interquartile range?
Both are measures of spread or dispersion.
