Star plots

By | June 18, 2014

How do you grade risks? How do you decide which project to start next? You probably grade risks on a scale of high, medium or low and you probably choose projects based on the ‘value’ that they will deliver.

The problem is, these simple scales are often thought of as linear, when they actually have multiple variables.

Let me use a simpler scenario to explain. Imagine that you are looking to buy a new house. You are likely to consider a variety of factors that are all important to you: price, location, number of bedrooms, layout, condition of the property, size of the garden, etc. You view a number of properties:

  • Property A is valued at 450k, has 2 bedrooms, a good location, poor layout, good condition, small garden;
  • Property B is valued at 500k, has 3 bedrooms, a reasonable location, poor layout, average condition, tiny garden;
  • Property C is valued at 470k, has 2 large bedrooms, a reasonable location, reasonable layout, good condition, a tiny garden;
  • Property D is valued at 460k, 2 bedrooms, a reasonable location, poor layout, average condition, small garden.

Which is the best property? In this scenario, it would be difficult to use a simple five point scale to compare properties.

A star plot (aka a Kiviat diagram, radar chart, spider chart) allows you to compare data that has multiple variants, the result being a shape rather than a score.

Star spots

Example star plots for our house hunting example

 

I like the idea of using star plots for a number of reasons: firstly, it makes teams and businesses (or individuals) identify what is valuable to them before they even start looking at the data; secondly, visualising data helps decision-making (e.g. easy to spot when one option is eclipsed by another, easy to identify similar options, easy to spot outliers).

Star plots are not new (they date back to the 1800s) and are not without their critics, but I see most people using meaningless scales for managing risk and evaluating priorities, so I think they deserve a bit more attention.

 

Do you use star plots? If so, we’d love to hear your experiences. Has anyone used them for non-work decisions? Rating restaurants or hotels? Wedding venues? Potential partners?!

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