Likert Scales and One Number Reporting

Posted 03.15.11 by in: Know How 2 Responses

Last time I talked about reporting matrix data in “Discovering Different Ways to Report on Matrix or Table Data”. In that article, we found that a matrix of Likert scale questions is a useful survey question and we explored ways to report the resulting data.

Now, we’ll look at what happens when we add another dimension, time. (I’ll look at yearly data here, but it could just as easily be monthly, quarterly or any time period.) With the added dimension, things get cluttered pretty quickly. Let’s look at the Stacked Bar Chart when we add just one year.

All the information is there but it is cluttered. I.E – it is not easy to take it all in at a glance. This compromises the real value of the graphical display. Further, it won’t stay this way as time marches on! The problem quickly becomes untenable.

One thing we may decide to do is to drop the individual attributes and look at just Overall Satisfaction. One could argue that it is the most important anyway. See figure 2 below.

This is not too bad for looking at ten years, but it isn’t exactly crisp.

Enter One Number Reporting (ONR). Wouldn’t it be nice if there were a single number that we could track that tells us how we are doing? This is a frequent request of management and has been for many years.

Since the goal is to reduce the five levels of our Likert scale down to one, we won’t expect any measure to work perfectly.

Here are four ONR options:
1. Averages – The average rating after assigning numbers to the Likert scale levels; 5=Very satisfied, 4=Satisfied, 3=Neutral, 2=Dissatisfied, 1=Very unsatisfied.
2. Top two box percent – The sum of the top levels in the Likert scale (in Figure 2, the sum of the orange and blue boxes).
3. Net Promoter* Score 1 (NPS1) – The top box (blue) minus the bottom three boxes. [This was originally designed for the one question, “Would you recommend us to a colleague with similar needs?” the Net Promoter Score is the total who are “Very likely” to recommend you minus those who are neutral or unlikely to recommend you. The theory is that gives you “Promoters minus Detractors”.]
4. Modified Net Promoter* Score 2 (NPS2) – Percent satisfied (Very satisfied or Satisfied) minus (Very dissatisfied or Dissatisfied).

Below are charts of each option using the same data that appears in figure 2 above.



All four options yield similar pictures, so that’s good! As I mentioned in my last article, I’m not a big fan of the using averages because the number itself is hard to interpret, but any of the other three seem equally good.

So what does all this get us? For one, we have that “one number” for management that we can use to track progress over time with relative ease.

Secondly, we can add back the attributes we dropped from the attribute satisfaction we looked at in Figure 1. We now have a way to look at all the attributes over time using the so-called “spaghetti chart” (see below).

This chart let’s you look at trend data for several attributes at once. It can get a little cluttered but proves to be a useful data display tool. I am a big believer in looking at data over time. Looking at data over time allows you to build knowledge for improving your decision-making. Next time I’ll take a close look at analyzing trend data.

*Net Promoter is a registered trademark of Satmetrix Systems.

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About the Author

Ed Halteman - A SurveyGizmo Survey Expert
Ed has a master's degree in applied mathematics and a Ph.D. in statistics, and he has specialized in survey design for over 10 years. Ed currently heads Survey Design and Analysis (SurveyDNA.com) founded in January 2003 and is available for comprehensive survey design and analysis services. Contact Survey Design & Analysis for help getting more out of your next survey.

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