Chapter 3 Measures of Shape

A measure of shape can tell us how symmetrical or asymmetrical a set of data is. Skewness is a measure of shape, and can be negative (skewed to the left, or negatively skewed), 0 (symmetrical), or positive (skewed to the right, or positively skewed). This can be demonstrated via the histograms below:

It is also useful to know whether our data are unimodal (one mode), bimodal (two modes), or multimodal (more than two modes). For example:

Ascertaining the modality of a distribution can be useful for a number of reasons. For example, if we identify that a distribution is bimodal, it can indicate to us that there could be two distinct groups within the data.

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These notes have been prepared by Amanda J. Shaker. The copyright for the material in these notes resides with the author named above, with the Department of Mathematics and Statistics and with La Trobe University. Copyright in this work is vested in La Trobe University including all La Trobe University branding and naming. Unless otherwise stated, material within this work is licensed under a Creative Commons Attribution-Non Commercial-Non Derivatives License CC BY-NC-ND