1. The centreline (CL) on a Run Chart is the Median
Elements of a Run Chart
The centreline (CL) on a Run Chart is the Median
Measure ~
X (CL)
Time
Four simple run rules are used to determine if special cause variation is present

2. Source: Swed, F. and Eisenhart, C
Source: Swed, F. and Eisenhart, C. (1943) “Tables for Testing Randomness of Grouping in a Sequence of Alternatives.” Annals of Mathematical Statistics. Vol. XIV, pp , Tables II and III.

3. Non-Random Rules for Run Charts
A Shift:
6 or more
A Trend
5 or more
Too many or too few runs
An astronomical data point
Source: The Data Guide by L. Provost and S. Murray, Jossey-Bass Publishers, 2011.