Measures which involve timing events locally on participants own equipment are subject to uncertainties not present in centrally controlled environments. This document details and quantifies some of these uncertainties.

This resource can be downloaded or viewed using the link: JavascriptTiming.pdf

If you have wget available (typically on linux systems), then you can also obtain a copy using the command

 wget  -nd  biobank.ctsu.ox.ac.uk/ukb/ukb/docs/JavascriptTiming.pdf