What Is a Median-Median Line?

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The median-median line, like the least-squares line, is a line calculated to fit a collection of data. It differs from the least-squares line in being more resistant to outliers and being easier to calculate. Here’s how it’s found: Divide the data along the horizontal axis into three equally sized groups. Find the median x- and y-values for each group (A, B, and C). Draw a line from A to C; this gives the slope of the median-median line. Determine how far point B is from the line, and shift the line one-third of the way toward point B. This determines the line’s location or intercept.