The Truthful Art: Data, Charts, and Maps for Communication (Paul L Papagiannis' Library) by Alberto Cairo

Author:Alberto Cairo
Language: eng
Format: epub
Publisher: New Riders
Published: 2016-05-05T04:00:00+00:00

The Variance and the Standard Deviation

Any data analysis software can calculate a standard deviation for you faster than a frog zaps a fly with its tongue, but it’s important to understand where that statistic comes from. So let’s take a look at a handful of simple formulas.

To calculate the standard deviation, we first need to find the variance, a statistic that is quite useful for confirmatory tests.2 Figure 7.3 shows the formula for the variance with some explainers to clarify its elements.

2 You may have heard of ANOVA, which means “analysis of variance.” This test is useful to analyze if the differences between the means of several groups of scores (say, test scores from several schools) are noticeable enough.

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