Standardization of Scales in Survey Analysis
Posted by Jeffrey Henning on Wed, Jun 17, 2009
While I believe that the scales with the highest reliability and validity are 5-point unipolar scales and 7-point bipolar scales, and I prefer using fully labeled scales, that is for gathering information from respondents. Presenting information to users of your survey research is a different matter. Simply presenting scales designed for accurate data collection may not facilitate ease of understanding of the results.For instance, since 7-point scales are rare in business use, readers of your report may have difficulty understanding the results if you use a 7-point scale. If you are using a mix of 5- and 7-point scales when reporting results, you are certain to confuse some of your readers. If you are doing a cross-survey analysis where similar questions in different surveys used different scales (see Standardize Your Customer Satisfaction Questions & Rating Scales), you will definitely want to standardize your scales.
For presenting data, I typically prefer to map scales to a 0-10 scale. I find that the business professionals I present to intuitively understand this scale. The broader range of values also makes it easier for readers to see differences in the results.
For instance, I would typically not present the following, even though this is an accurate representation of the gathered results.
Rating of Attributes on a 1-5 Scale
from 1 = Not at all important to 5 = Extremely important
| Functionality of product | 4.7 |
| Product learning curve | 4.6 |
| Quality of technical support | 4.4 |
| Ability to grow with product line | 3.9 |
| Price of product | 3.6 |
| Availability of free trial | 3.5 |
| Helpful sales representative | 3.4 |
| Third-party reviews of product | 2.9 |
| Customer list of vendor | 2.7 |
| Vendor’s brand name | 2.5 |
On a 1-5 scale, the midpoint is 3.0, not 2.5 (which would be the midpoint of a 0-to-5 scale). To calculate the midpoint, simply average the lowest and highest ratings: for instance, (1+5)/2 = 3.
Instead of presenting the above, I standardize the results to a 0- to 10-point scale. Standardization from a 5-point scale is not simply a matter of doubling the answers; doing that would produce ratings from 2 to 10. The 11-point scale has more than twice the granularity of a 5-point scale. Instead, map the scale to a 0-to-1 scale: (X-1)/4 produces a number from 0.0 to 1.0 for each rating. Then map this to a 0-10 scale, so (X-1)/4*10 results in the new scores.
Rating of Attributes on a 0-10 Scale
from 0 = Not at all important to 10 = Extremely important
| 0-10 Scale |
| Functionality of product | 9.2 |
| Product learning curve | 9.0 |
| Quality of technical support | 8.4 |
| Ability to grow with product line | 7.3 |
| Price of product | 6.6 |
| Availability of free trial | 6.3 |
| Helpful sales representative | 6.0 |
| Third-party reviews of product | 4.7 |
| Customer list of vendor | 4.1 |
| Vendor’s brand name | 3.8 |
Standardizing bipolar scales typically involves mapping them to a –X through +X range. For instance, from -3 through +3 for a seven-point scale to -10 through +10.
Remember, your job as the survey analyst is not to provide an in-depth, detailed view of all the data collected, as it was collected. Giving someone a spreadsheet of all the survey responses would do that. Your job as a survey analyst is to tease out the most important information and present to it your readers in an fashion that will maximize comprehension and understanding. And one tool to accomplish that is standardizing scales for presentation purposes.