Brownian thought space

Cognitive science, mostly, but more a sometimes structured random walk about things.

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Location: Rochester, United States

Chronically curious モ..

Saturday, August 01, 2009

Probability of finding a four-leaf clover

Short answer: around 1 in 2,000.
(Clarification: this is the probability that, if you pick up a single leaf at random, it will have four leaflets.)
Here is my collection of four four-leaf clovers (out of five, the fifth has shredded leaves), collected over a period of two weeks.
If you look at the wikipedia page (& refs therein), the most commonly cited figure is 1 in 10,000. Unfortunately there are no actual observations reported anywhere.
But now I can report that, according to my very empirical research, the probability of finding a four-leaf clover is probably more like 1 in 2,000.

How do I know?

  1. I find that I can scan around 100 plants per minute.
  2. Most recently, I found two four-leafs in about 30min worth of scanning.
  3. This gives a rate of 1 in 1,500
The previous attempts have however been slightly longer, although I didn't time them as accurately. Also, the actual number of plants scanned per minute can vary due to wandering attention. So, I would think a more conservative estimate is ~1 in 2,000.
Of course, these are all in upstate NY, although not at a single location. Perhaps these rates vary with a whole bunch of other factors.
Still, these are fairly low odds - finding 5 four-leaf clovers, even with these better estimates, is still less than one in 10 quadrillion! (Clarification again: this is the probability that, if you pick five leafs blindly, all five will have four leaflets each.)