Shamelessly stolen from REALITY 2.0 by Doc Searls.
(You know the web, page here today, gone tomorrow. If I just have the link, you may not be able to appreciate the image in the future)
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Producing Alternative Means statistics with SQL
MySQL’s built-in AVG() computes the arithmetic mean — the sum divided by the count. That is the right default for many questions, but it is not always the right measure of central tendency.
Extending MySQL Capabilities with UDFs, Plugins and Components
MySQL offers three different approaches to extending the SQL capabilities with the default product you download and install. These are: User Defined Function (UDF) MySQL Manual MySQL Plugin MySQL Manual MySQL Component MySQL Manual For the purposes of this post I will be using the current LTS version MySQL 8.
Producing One-Sample Z-Test statistics with SQL
The one-sample Z-test determines whether a sample mean differs significantly from a known population mean when the population standard deviation is also known. It is the appropriate test when the population parameters are established — quality control benchmarks, national averages, long-run process measurements — and you want to evaluate whether a new sample is consistent with them.