Why my CTR is 200%

1 impression 2 clicks

[jimpoo]

I'm surprised to see one of my ads' CTR is 200%,
the report shows 1 impression, 2 clicks, 200% CTR, how could this happens?

[diamondgrl]

Yes, please, can I hire you at once? I would like 200% CTR.

Actually, wait a day or so to see what happens to the stats. They're kind of screwy.

[IntegraGsrBalla]

Could it be that the user clicked on your ad, pressed the back button and clicked on it again?

[jimpoo]

I went to check my account again, it is 33.3% now

[jimpoo]

A question.

We say Position = Maxium CPC X CTR

Does google use today's CTR or accumulative CTR to apply to the formula?

And what default CTR value when google is going to deliver a new ad?

Thanks.

[eWhisper]

Google takes into account all time CTR and last impression CTR, with more weight given to the last 1000 impressions.

So it's really (this is not the formula, just an example)
((all time CTR x 0.4) + (last 1000 CTR x 0.6)) x (max CPC)

The default value is the average for all advertisers using that exact keyword (and match option).