Questions / Quant trading, Counting & stopping
Match two independent counts
Two players independently toss two fair coins each. What is the probability they obtain the same number of heads?
Answer it in the app It's free. You get hints, a second try if you miss, and a follow-up question.
Show the answer and worked solution
Answer: 37.5% (3/8)
- The count probabilities are 1/4, 1/2, 1/4. Matching has probability 1/16 + 1/4 + 1/16 = 3/8.
Interview shortcut. Σ P(k)² over 0, 1, 2 heads: 1/16 + 4/16 + 1/16.
In the app this has a follow-up where one thing about the setup changes. Try the follow-up.