Plot for Thought

I am old enough that I have both observed and given presentations on clear film with an old school overhead projector. I was thinking about time and visualizing time and studying statistical process control and using charts to help with decision making. Suddenly, I had a perfectly clear visual of a stack of overhead film with run chart plots overlaid with each other for comparing data.

Statistical Process Control, specifically Run Charts (a line graph where a measure is plotted over time), are useful tools that allow us to:

  • Display data to make process performance visible
  • Determine if a change resulted in improvement
  • Assess whether improved performance has been sustained

What does that have to do with my overhead projector moment?

Let’s use a legal example. Perhaps I want to see my time working in one practice area compared another. A run chart will help me see if there are patterns. If I have some data (which is available in my time and billing system), I could plot that in a run chart. Comparing data in an overlay format works well if you can keep the scales for the charts the same. If the scale is too dissimilar, I can reformat the data by showing both sets as percentages of a whole. If I have lots of data, I can plot averages or rational subgroups.

Maybe I just want to compare my billable time before and after an event (hiring staff, new client group, research questions answered in CanLII vs. a fee based service. It is pretty easy to make a chart in Excel and visualize data.

Line Plot
What is the point (pun intended). Plot points that appear on a visual chart are much easier to pick out than if you are looking at a list of numbers. Visualizing data makes decision making based on that data an easier task.

There is a quick guide to recognizing shifts and trends at this site. There is also a good guide to various types of control charts available.

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