Say you have a campaign and consistently see click-through-rates of 10% over a long period of time. Can you use that data to accurately predict whether the same thing will occur in the future? This question is being asked and discussed at WebmasterWorld.
I would say that it is tough to make any determinations because the market is volatile. There is a lot of change that can occur and you can't definitively say with full confidence that the future will hold the same results. This is apparently a notion echoed by a member on the forums:
i'd say that because the market is not a stable laboratory atmosphere where many things are held constant, predicting things using classical science and statistics is a problem. too much can change that you can't control, so why calculate any precise future confidence levels in predicting an outcome.
Some others see similar fluctuations such as seasonal change and occasional drastic "bumps." The advertiser is advised to carefully monitor these anomalies rather than consider it a gamble.
Any huge plan (like some kind of investment) would need a careful examination.
Forum discussion continues at WebmasterWorld.