Why not average ? Everyone gets ups and downs on their clicks. It is just noticeable when you are talking abt low number of samples, and the earnings will be skewed. Unless you are showing same site with 1000 clicks showing very drastic changes in earnings, then we have something to discuss.
Perfectly normal fluctuations. Forget them and concentrate on improving content. Do you really care about a few Cents anyway? If it was 1000 clicks at 1 cent each then I would worry.