How many impressions is a good sample?

How many impressions is a good sample to determine effectiveness?

[ken_b]

How many impressions is a good sample to determine the effectiveness of adsense layouts and color options?

I recently changed the adsense color/border scheme on my pages and am wondering how many impressions is a reasonable number to determine if such changes are postive or not.

I left the changes in place forabout 50,000 impressions (that's normally 2-3days on my site) and the made an adjustment. But I wonder if that is really a big enough sample.

[europeforvisitors]

It's probably an adequate sample if you noticed dramatic differences in CTR, but not if you noticed only slight differences that could have reflected day-to-day variations.

Also, if your CTR tends to be higher on some days of the week than on others, you might want to leave the changes in place for a couple of weeks so that you can compare Monday to the previous Monday, Tuesday to another Tuesday, etc.

[onfire]

A week at min, a month to get a bigger snapshot and enough data to check against, but just when you think your seeing a pattern - change - improvement and all seems settled, bang...... it changes.

[jomaxx]

It sounds like enough, but the more important statistic is how many clicks you got during that period (which you can't tell us because it would give away your CTR - haha).

In other words, 250 clicks isn't really enough. 2,500 clicks is probably a pretty good sample to make decisions on.

[ken_b]

Jomaxx

>>how many clicks<<

Well, yes, I was thinking about the number of clicks involved. Let's just say the change was noticably negative, even on a relatively short term trial.

Thanks.