On the evidence of a single coin toss

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Tags: probability, evidence, reasoning, bayesian, coin-toss-problem

Say that you bump into me at the coffee shop. After saying hello, I hand you a coin and claim that it’s special: when flipped it always comes up heads. You inspect it and say that it looks like a normal coin.

“Seriously, it always comes up heads,” I say. “Flip it.”

You flip it. It comes up heads.

Now, here’s my question to you: After seeing the outcome of this single coin toss, how much more should you believe my claim that the coin always comes up heads, compared to what you believed before the coin toss? In other words, how much should this single toss sway your prior beliefs about my claim? Should it sway you at all?

Post your thoughts in the comments.

I’ll provide the answer later.

Update: For my answer, see part two: More on the evidence of a single coin toss.