Notes on the Pre- and Post-Survey

The Pre-Post survey is used to look at how things may change over time. It may be how brand awareness levels change after a new ad campaign is introduced or how opinions of a political candidate move after a speech. The catalyst to potential change, sometimes called the event or treatment, is a known, planned treatment that usually happens within a certain timeframe. If this is the case, then a Pre-Post project may be applied.

There is a unique challenge to Pre-Post research.

If it’s not done right you risk having murky data. In some cases, we have to live with the ambiguity, but it’s best not to if possible. The challenge relates to the sample frames. One frame is ideally a control group. A control group is a stand-alone group that is not exposed to the treatment (for example advertising, public relations, sales promotion and so on). The other frame represents those who are exposed. Let’s call this our normal sample. The really important thing to realize is this: If there is no control, we won’t have the best possible situation to calculate the change.

Getting started, the Pre-study must be done before the treatment is applied.

Let’s say it’s an ad campaign for a new product. The Pre-study must be done before the campaign is released to establish the baseline. Remember, the Pre is done against both the control and normal samples. After the Pre is done, you’ll have the baseline for both groups and then the treatment is applied. If the treatment process is out of your control, remember to advise your partner that there is to be NO treatment against the control. The control group needs to remain isolated as much as possible from the treatment.

After the treatment is completed there will be a Post study of the same groups. Presumably, those in the group who received the advertising will report a higher level of awareness. However, it may also be that those in the control, those not exposed to the ad campaign, also report a change in awareness. This change can be attributed to “noise.” Perhaps control members heard about the product by word of mouth? In any event, there invariably is noise-it’s to be expected.

Pre survey awareness: Normal group, 32%
Pre survey awareness: Control group, 31%

Post survey awareness: Normal group, 40%
Post survey awareness: Control group, 33%

Rate of change in Normal: +8%
Rate of change in Control: +2%

In this example, you can see awareness in the Control increased despite not being exposed to the treatment. However, the value of having the Normal and Control permits you to get something to go on and not necessarily breaking the bank in the process.

If you are considering a Pre-Post study, keep in mind one of the most important elements of the project is having a baseline from which to measure change and the control to get a truer measure of the impact the event or treatment has. Finally, please realize this can be complicated stuff and you may wish to consult with a reliable research pro to help set up and administer your survey.

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