One of my favorite ways to look at data is by using a control chart. Typically control charts are used to evaluate data over time generated by a specific process. It is one of the Total Quality Management tools used in manufacturing to assess if a production line is in or out of control. But, another use of a control chart is to compare logically related observations taken at the same point in time. It is a quick way to determine which observations might be worth deeper consideration because they are behaving differently than the majority.
CREATE A CONTROL CHART IN 5 EASY STEPS
My 5-step process to create a control chart is simple and fast.
- Calculate the average score of the data set.
- Calculate the standard deviation of the data set.
- Set the upper control limit as the average + 1 standard deviation.
- Set the lower control limit as the average – 1 standard deviation.
- Plot the observations.
Any observations between the two control limits are considered “in control”. Typically, I don’t spend a lot of time on them. Observations above and below the control limits are what I focus on studying closer because their “aberrant” behavior often offers the best chance to learn something new.
If you have never used a control chart to analyze data, give it a try. It is one of the tricks I use to sort through a lot of data very quickly and prioritize where I dig deeper. Excel has a function for calculating both the average and standard deviation of a data set, so the math isn’t really complicated.
2012 AMERICAN DREAM STATE RANKING DATA CONTROL CHART
I thought it would be interesting to control chart the American Dream Composite Index™ (ADCI) scores of the states used in the 2012 American Dream State Ranking Report. This is one way to quantitatively determine states may be worth a deeper exploration to better understand why people living there feel they are meaningfully over or under achieving the American Dream versus national average.
Here are the results of the control chart exercise.
Click on the image to make it larger.
The next step would be to try and answer why these states over or under performed the majority of states. I am publishing a series of case studies that compare the states based on the scores of the 35 dimensions that comprise the overall ADCI. The case studies look at published information for insight. But, the best way to understand why is through local market research to identify the specific drivers behind the sentiment. I am hopeful state economic development organizations will consider launching such research, particularly the states that are below the lower limit in the control chart. This type of study is not complicated. It can be designed and executed by any reputable market research firm.
Have you had any experience in using control charts? What tips can you provide on when and how to use them? Are you surprised by the states listed above and/or below the control limits?
So, which states offer their residents the greatest chance of living the American Dream to the fullest, and which states are lagging behind?
To view the complete set of State rankings based on the ADCI and five explanatory sub-indexes, simply click this button