It is very, very important how targeted the word and the ad are (IMO)
Ex: if one searched for "red nice metal widgets" - and your ad is "widgets" , your CTR would be smaller than CTR for the "Red nice metal widgets" title.
Some figures could be 15 - 10 - 6 - 4 - 2 -1If this would be for one of your words+ad, it says nothing for another combination of words+ad.
I doubt anyone could give exact numbersI did it here (msg #5):
But I also think, that It depends on many other specific factors, so you cannot do any general conclusion from those numbers.