Waves ........the bell curve......m = 0..slope is zero....half way through...

68–95–99.7 rule - Wikipedia

https://en.wikipedia.org/wiki/68–95–99.7_rule

In statistics, the 68–95–99.7 rule, also known as the empirical rule, is a shorthand used to remember the percentage of values that lie within a band around the ...

‎Cumulative distribution ... · ‎Normality tests · ‎Table of numerical values

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