Change over time

Run chart

Shows observations in run or time order, usually around a median reference.

What it answers

Does the process show sustained patterns over time?

The question

Is the average call waiting time stable from week to week?

Points for weeks 1 to 14 around a median of 52.5 seconds. The last five weeks all sit above the median, a sign of a shift.

Illustrative data. It belongs to no company.

Initial process monitoring without calculated control limits.

When formal control-limit signalling is required.

Follow observations against the centre line and inspect runs or shifts.

Unlike a control chart, it does not require statistical control limits.

Layout: Long table
Fields: Time: date/datetime or ordered number; Value: number
One row is: One observation at a time or ordered position. What is the grain?
Rules: Parse dates consistently and sort ascending. Resolve duplicate timestamps by a declared rule. Missing values are not automatically zero.
Optional: Optional Series. Use regular spacing for methods requiring it.
Preparation: Preserve observation order, choose a valid centre line such as the median and apply stated run-chart conventions.
Units: Time uses a stated date/time unit and sampling period; the value axis uses the measure's unit. Rates need their own explicit denominator.

A long table: one row per observation, few columns. New data adds rows.

Data 10,11,12,9,10 gives median 10. Plot in order with that reference; the short example demonstrates reading, not a reliable process rule.