Hello there people! Sorry for being so quiet. Lots and lots of travelling has been done. I am a little more settled this month so expect some more wisdom (?) to be imparted through this blog over the next few weeks. I just wanted to have a quick rant…. and it is about data. Or rather the way people interpret changes in values over the short term…. (I think many of you see where this is going)
These days everyone likes to talk a lot about making decisions with data. Unfortunately everyone who says this rarely understands the data that they see in front of them. I haven’t got good graphics at the moment to demonstrate these points so bare with me. I will add some later.
Usually data graphs are generated in excel and will look like a month by month value plotted on an over-sized scale. What does this tell us? Well it can tell us over time what trend we are dealing with. If I plot turnover per month for a full year I can get an idea whether it looked reasonably stable or not (?) or at least see if it is trending upwards or downwards. Usually upwards is preferred in this case! But how do I know if it is stable or not? If those month by month variations are small compared to the absolute value, how do I interpret them? If I am not looking at a large data set or rather a value month by month or week by week how do I know what the trend is or will be? Unfortunately, these are questions that are rarely rarely asked, but they should be.
I would suggest that if you do not know at the top of your mind what the answer to the above questions is you check out what a control chart is. There are lots of great resources online and on amazon for these. Wheeler wrote what many consider to be the premier books on the subject. The principles are very simple and easy to follow and despite what many people tell you, you don’t need minitab to draw them. I prefer a pencil, ruler, calculator and graph paper myself! Check it out, see what you think and let me know if it helps!