What does a small interquartile range mean?
I have to disagree with the first poster. The size of the interquartile range should *not* be a measure of the sample size. I seem to remember that it’s an unbiased estimator. The interquartile range is a measure of the “central tendency” just like the standard deviation. Half the data points lie within the interquartile range (and that’s true whether you have 20 measurements or 10,000). A small interquartile range means that the data are very consistent (most values lie close to each other). The advantage of the interquartile range over the standard deviation is that the interquartile range includes half the data points regardless of the shape of the distribution. The most common uses of the standard deviation, on the other hand, require that you assume a normal distribution. The median is the number in the middle of the distribution. Half the data points lie above it, and half lie below it. For a symmetrical distribution, the median will lie halfway between the first quartile and the
