Don’t be so sure that the Boston Marathon is slowing down: Jumping the gun when it comes to data point mentality.
As the 121st Boston Marathon launches on April 17, recent evidence may suggest that winner of the world’s oldest annual marathon is slowing down. The 2015 men’s open winner was 40 seconds slower than in 2014. And the 2016 men’s open winner was almost three and one-half minutes slower than 2015. Do we need any further proof that the winning time is getting longer?
We, at PQ Systems advocate looking at data over time. Point mentality, or looking at only one data value compared to the previous, is almost pointless when additional data is available. Consider the finishing times in the men’s open division for the past twenty years shown in the chart below. Based on this data, it is safe to conclude that the times are not increasing… or decreasing. The finish times are all part of normal expected or common-cause variation.
Over the life of the race, the chart below shows how the process has improved (the winning time is quicker) over the years and seems to have stabilized in the last 20 years with an average time of about 129 minutes.
Whether you are manufacturing parts for cars or caring for patients, trends in your data are not typically evident after just two or three measurements. Avoid point mentality that may stimulate a sky-is-falling reaction. The Boston Marathon has run for more than a century. Looking at long-term trends is easy when you have data like this.