Xcelsius Challenge for Community Poll Results

If you’re interested, you have until April 30, 2010 to enter your submission.

I’m thinking of creating a pie chart.

Here is a gauge:

Which is more effective? Which conveys more information, and why?

Digital Dashboards

Decades ago car manufacturers experimented with digital dashboards. Ever wonder why you don’t see more of them today? People hated them. Some newer hybrid cars are using more digital dashboards, but most of the cars on the roads today – even newer cars – have analog gauges. If any digital information is displayed it is generally a supplement to the analog information, rather than a replacement. Speedometers, tachometers, even fuel gauges still use analog-style displays.

Let me go back to the number and the image of the gauge that I opened the post with. The number 50 is just that, it’s a number. It is completely without context. It doesn’t tell me if that’s a high number or a low number. It doesn’t tell me whether it’s a good number or a bad number. An analog gauge can accomplish all of these things at once.

The number “50″ expects me to understand the context of the number and be able to make conclusions. If I make the wrong assumption, I end up with the wrong conclusion. The gauge helps remove those assumptions and ensure the correct conclusion. I am going to break the gauge down into components and show how they all work together.

Simple Gauge

This is about as basic as a gauge can get. There is a container and a needle and that’s it.

Even this most basic gauge contains some important information. Just by looking at the gauge I can see that the represented number is more than 50% of the gauge capacity. The needle is pointing slightly to the right of center, and by convention gauges fill from left to right. So without even knowing the exact number, I know that it is somewhere over half full.

Adding Tick Marks

For the next step I have added tick marks to my gauge. Here are a couple of versions of the gauge; look very carefully at the tick marks on each one.

Tick marks don’t get as much respect as some of the other gauge features, but they’re important. There are more tick marks on the gauge on the right than on the left. The implication is that the scale is higher and therefore more tick marks are required for precision. The gauge on the left goes from 0 to 95 and shows a value of 50. The gauge on the right goes from 0 to 950 and shows a value of 500. The percentage of 50 into 95 is exactly the same as 500 into 950 but the scale is different. The density of the tick marks can show that.

Good or Bad?

So far I have shown how a gauge can take a raw number (50) and put it into context. I know that 50 is above half, and I have an idea of the scale because of the tick mark density. The next question is whether 50 is a good or bad number, and that’s easily done by adding alerts.

With the green-yellow-red alert added to the middle of the gauge I now have a complex instrument that communicates all sorts of information. These colors are fairly standard, but someone with red-green color blindness might not appreciate them. There are also issues with any delivery method that does not include color. For online viewing the alert does a nice job of completing the gauge. I can now easily derive all of the following bits of information from this simple gauge:

1. The number is more than 50% of the total scale
2. The scale is relatively small as denoted by the density of the tick marks
3. Higher numbers are bad, as shown by the fact that upper numbers are in the “red” range
4. Most of the potential gauge numbers are good, as shown by the broad range of “green”

Final Gauge

After showing how much information is conveyed by the graphical elements of the gauge, it might seem like extraneous information to show the actual value. But for some folks they might prefer to know the exact number rather than guessing what the gauge is showing. Xcelsius provides that option as well, resulting in this as my final gauge.

This gauge includes numbers for the upper and lower boudaries of the gauge, as well as the exact number represented by the position of the gauge needle.

Conclusion

Are gauges like the style I used in this post perfect? Clearly each gauge has strengths. When building a dashboard it is important to select the proper representation for each number, based on the information that needs to be conveyed. When I built my first web site (a very long time ago, in the time of AOL and dialup access to the Internet) I took an old phrase and updated it to this:

A picture is worth a thousand words… but a thousand words will download faster.

Today I might say this:

A picture is worth a thousand words… but only if it’s the correct picture.