When comparing sales increases over some preceding period, allowances must be made for situations that are not normal. For example, your experience may be than rain on the day an ad appears cuts its pulling power by 50 percent. Similarly, advertising response will be affected by the fact that your customers work in a factory that is out on strike. Keep repeating the process. Much advertising loses effectiveness because the advertiser doesn't keep reminding people.
Repetition help increase knowledge of and interest in, the product.
You can soon estimate how often you should repeat each ad - exactly or with minor changes. Then look for differences between the two classes. The time the ad was broadcast or run may be responsible for a particular response level. Other factors, however, may be just as influential as time or even more so, though in radio time is often crucial. Consider the message and how well it was expressed.