All About Run Charts

Run Charts are simple line graphs of data plotted over time. They are used to better-understand the performance of a process, as they help people distinguish between random variation and special causes, or to track information and predict trends or patterns.

A run chart can also reveal whether a process is stable by looking for a consistent central tendency, variation and randomness of pattern.

One of the most common CI tools, a run chart is easy to interpret and does not require tedious calculations or special software to produce.

Sample Run Chart

How to create a run chart:

    1. Identify the question that the run chart will answer and obtain data that will answer the question over a specified period of time. For example, if you were looking at how long it takes to complete a task, you will make note of the time taken (in minutes) to complete it over a specified period of time.
    2. Gather data, generally collect at least 10 data points to detect meaningful patterns.
    3. Create a graph with vertical line (y axis) and a horizontal line (x axis).
    4. On the vertical line (y axis), draw the scale related to the variable you are measuring. In our example, this would include the complete range of observations measuring time-to-completion
    5. On the horizontal line (x axis), draw the time or sequence scale.
    6. Plot the data, calculate the median and include into the graph.
    7. Interpret the chart. Four simple rules can be used to distinguish between random and non-random variations:
      1. Shift – 6 consecutive points above or below the median
      2. Trend – 5+ consecutive points going up or down
      3. Too many/too few runs – too few or too many crossings of the median line
      4. Astronomical data point – a data point that is clearly different from all others (often a judgement call)