When conducting a program evaluation or customer tracker (e.g., brand, satisfaction, etc.), we are often collecting input at two different points in time and then measuring the difference. While the concept is straightforward, the challenge is keeping everything as consistent as possible so we can say that the actual change is NOT a result of how we conducted the survey.
Because we can be math nerds sometimes, take the following equation:
A change to any part of the equation to the left of the equal sign will result in changes to your results. Our goal then is to keep all the survey components consistent so any change can be attributed to the thing you want to measure.
- Asking the same questions
- Asking them the same way (i.e. research mode)
- And asking them to a comparable group
Let’s look at each of these in more detail.
Asking the same questions
This may sound obvious, but it’s too easy to have slight (or major) edits creep into your survey. The problem is, we then cannot say if the change we observed between survey periods is a result of actual change that occurred in the market, or if the change was a result of the changing question (i.e., people interpreted the question slightly differently).
Should you never add or change a question? Not necessarily. If the underlying goal of that question has changed, then it may need to be updated to get you the best information going forward. Sure, you may not be able to compare it looking back, but getting the best information today may outweigh the goal of measuring change on the previous question.
If you are going to change or add questions to the survey, try to keep them at the end of the survey so the experience of the first part of the survey is similar.
Asking them the same way
Just as changing the actual question can cause issues in your tracker, changing how you’re asking them can also make an impact. Moving from telephone to online, from in-person to self-administered, and so on can cause changes due to how respondents understand the question and other social factors. For instance, respondents may give more socially desirable answers when talking to a live interviewer than they will online. Reading a question yourself can lead to a different understanding of the question than when it is read to you.
Similarly, training your data collectors with consistent instructions and expectations makes a difference for research via live interviewers as well. Just because the mode is the same (e.g., intercept surveys, in-class student surveys, etc.) doesn’t mean it’s being implemented the same way.
Asking a comparable group
Again, this may seem obvious, but small changes in who you are asking can impact your results. For instance, if you’re researching your customers, and on one survey you only get feedback from customers who have contacted your help line, and on another survey you surveyed a random sample of all customers, the two groups, despite both being customers, are not in fact the same. The ones who have contacted your help line likely had different experiences – good or bad – that the broader customer base may not have.
So, that’s all great in theory, but we recognize that real-life sometimes gets in the way.
For example, one of the key issues we’ve seen is with changing survey modes (i.e., Asking them the same way) and who we are reaching (i.e., Asking a comparable group). Years ago, many of our public surveys were done via telephone. It was quick and reached the majority of the population at a reasonable budget. As cell phones became more dominant and landlines started to disappear, while we could have held the mode constant, the group we were reaching would change as a result. Our first adjustment was to include cell phones along with landlines. This increased costs significantly, but brought us back closer to reaching the same group as before while also benefiting from keeping the overall mode the same (i.e., interviews via telephone).
Today, depending on the exact audience we’re trying to reach, we’re commonly combining modes, meaning we may do phone (landline + cell), mail, and/or online all for one survey. This increases our coverage (http://www.coronainsights.com/2016/05/there-is-more-to-a-quality-survey-than-margin-of-error/), though it does introduce other challenges as we may have to ask questions a little differently between survey modes. But in the end, we feel it a worthy tradeoff to have a quality sample of respondents. When we have to change modes midway through a tracker, we work to diminish the possible downsides while drawing on the strengths to improve our sampling accuracy overall.