4.3. The Shape of Distributions


Shape is a third important property of a set of measurement data. Shape is the pattern of distribution of the data. You can use either a histogram or a dot plot to study the shape of a distribution of data.

A distribution will either be symmetrical, when low and high values balance each other out, or skewed, not symmetrical and showing an imbalance of low values and high values. To determine the shape of a data set, you compare the mean with the median. If these two measures are equal, the CTQ or X is considered to be symmetrical (or zero-skewed). If the mean is less than the median, the variable is called negative, or left-skewed. If the mean is greater than the median, the variable is described as positive ...

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