Cumulative sums are not independent

A financial news site said Chinese coronavirus figures were “too perfect to mean much”.

A severe statistical misunderstanding underlies this complaint. Cumulative sums are, by definition, not independent observations. This article shows how cumulative sums of pseudo-random data are also ‘too perfect’ by the same measure.

It all adds up

--

--

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store