Two Wrongs

Guess ≠ Prediction ≠ Bet

Guess ≠ Prediction ≠ Bet

This is one of my many pet peeves: people confusing guesses with predictions and bets.

You will think this is nitpicking, and you’re probably right. The way I define these terms is also not universal, but all I ask of you is to separate these three types of speculation, because they are fundamentally different from each other. This is important to me because real bets are an important social mechanism when people have different beliefs in things.


“I think Ghana will win this game of sportsball,” is a guess.

“I think Ghana will win this game of sportsball, and I’m 70 % confident,” is a prediction.

“I think Ghana will win this game of sportsball, and whoever thinks I’m wrong can either give me $10 now and receive $14 if I’m wrong, or get $10 from me now, and give me $14 later if I’m wrong,” is a bet at the same confidence level as the previous prediction.

What Is a Bet?

Evidence is used to settle debates about facts – bets are used to settle debates about beliefs. Or rather, bets allow different beliefs to peacefully coexist. Betting is what makes differences in belief profitable instead of frustrating.

Bets can also be used as protection against being wrong: you don’t think your house will burn down, but getting fire insurance is a bet that your house will burn down. That way, in case you were wrong about the house not burning down, you lose your home but at least you get the payout from winning the bet.

If you say “I bet it’s gonna rain tomorrow” then you need to be prepared to answer “what odds are you offering?”

A bet is an exchange of stuff conditional on an uncertain outcome, with the exchanged amount under the different outcomes determined in advance.

Additionally, if you’re claiming to offer a fair bet (i.e. the odds accurately reflect your belief in the outcome) you must be willing to take either side of the bet. In other words, if you say “give me $10 now, and I’ll give you $17 if it rains tomorrow,” I can say, “I don’t think so. Why don’t you give me $10 now, and I’ll give you $17 if it rains tomorrow.” If you refuse, I know your proposed bet was designed to screw me over and didn’t actually reflect your belief in rain tomorrow.

A bet, in a sense, is a way for multiple people to quantitatively challenge each other’s beliefs in things. But it includes multiple people, and it’s about conditionally exchanging stuff quantified in advance.

This goes also for sports results. “I bet the game ends 7-7” means nothing unless you specify what odds you’re offering, i.e. how strongly you believe in that outcome.

What Is a Guess?

A guess is in some sense a statement of which outcome you find most likely.

“I guess it will rain tomorrow” or “I guess the game will end 2-1” are guesses, and statements of the most likely result.

The drawback of guesses is that they’re not really open for criticism. People can disagree on what’s most likely, but a guess has no mechanism for settling those differences. However, throw in odds and it becomes a bet which is open to be challenged.

What Is a Prediction?

A prediction is a bet without the exchange of things.

You guess an outcome, you specify a quantity of stuff you would hypothetically be willing to exchange, but you never actually agree with anyone to exchange anything. This property means that predictions in some sense are the worst of both worlds: they are as complicated as bets, but as open to challenge as guesses.

The exchange-free nature of predictions often lead to the quantities being expressed as the inverse of odds, which is probability. Probability is a rather abstract idea, but it’s practically the same as odds.

This means a prediction might sound like, “I think there’s a 60 % probability of rain tomorrow.” (This is the same as the 10:17 bet you saw previously, except stated as a percentage.)

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