Line Charts vs. Column Charts for Metrics & Lean Daily Management
One topic that I didn't have time for in today's workshop is a relatively minor point, but something I wanted to get your thoughts on.
I'm talking about the use of “bar charts” vs. “line charts” when tracking performance measures through Lean Daily Management, Strategy Deployment, or other methods.
More often than not, when I see Lean Daily Management boards in my visits, I see more of what's commonly called “bar charts” than anything, like this:
Most people call them “bar charts,” but the technical term for vertical bars is “column charts” (as they are called in Excel). Bar charts have bars that run horizontally, instead of vertically.
Back to the chart above… don't get me wrong… I'd rather see daily metrics being charted in ANY way, rather than not at all — or being charted monthly, which is far too infrequent to be used for much improvement. This is probably in the category of nitpicking instead of more meaningful criticism – such as the times when people interpret charts badly (one of the themes of today's webinar).
When I was taught to track performance measures, it was always as line charts.
For one, they're easier to draw when done by hand (and I sometimes happily see this in hospitals). It's an outgrowth of drawing Statistical Process Control (SPC) charts by hand on the factory floor (as I saw at GM, even before anything Toyota/Lean was being adopted).
Secondly, I think line charts are better for reading and seeing trends.
I subscribe to the view that's shared in the helpful book Meaningful Graphs by James M. Smith, PhD.
“Column charts are primarily used to convey data on discrete categories (hospitals, wards, clinics, etc). They can also be used to display data over time periods but only for a limited number of time periods [up to 8].”
Here is an example of what I think (and Smith would agree) as a good use of a column chart – a static comparison in a point in time… it's a good use of a column chart in the wild, comparing the ratings of (I think) different physicians. Again, this is a snapshot in time, not a time series.
“Line charts are ideal for showing trends over time or successive events. They can be used for either short or long time periods.”
When used to show a time series (or, in this next case, two), I think column charts do more than just waste printer ink. I think they hide and masks trends that we need to carefully evaluate and react to (again, as I'll discuss in today's webinar).
If you're using column charts, I'm not condemning you (again, the interpretation over time is more important). You might have been taught to do it that way. Or, you saw examples.
Excel takes some blame, as it nudges you to create column charts, as that's listed before the line chart option, in the top menu or the chart “wizard.”
I think a line chart shows trends much more clearly if we're going to “eyeball it.”
Better than “eyeballing it” would be the use of relatively simple statistical methods as, again, I'll discuss in today's webinar.
What do you use or see in charts in your organization? Column charts or line charts?
Do you think it makes a big difference in seeing trends and interpreting the charts? Is this post a big deal over nothing?
Leave a comment and let me know what you think.