I see it quite often. Companies change something on their Google Adwords PPC campaign like (budget, CPC or ad) and they are ready to bring in the verdict in 2 days.

It would be wrong for me to put a stamp on a certain amount of days that you need to test as it all depends on your industry, traffic and buying pattern. For some even 24 hours is enough and for some 2-3 weeks are needed.

My advice is … if you’re doing anything to Google PPC campaign, note that you most likely will take a dip as Google looks at many factors before ranking your ad. On average try to give enough time to do a full 360 of your standard daily campaign. You need to compare the numbers to something so the most popular ones are Weekly tests (comparing the numbers week by week).

If you’re testing your AdWords Ad for higher Click Through Rate, Google allows you to have multiply ad variations running at the same time. Before drawing a conclusion on your test, have at least a total of 300 clicks to look at CTR - click through rate.

Bottom line is … don’t panic. There are hundreds of different things that can effect your numbers. Ex. Time of day, season, holiday, trend, news, …