'Every leg you add lowers your chance of winning'
The payout goes up and the probability goes down, and the second half is the part nobody shows you. Two safe-looking picks are often close to a coin flip.
The math nobody shows you
Take three picks from three different games at 56%, 56% and 63%. Each looks comfortable. Together they land about 19% of the time. That is not a safe bet, it is a long shot with a friendly-looking slip.
Now the mistake almost everyone makes. When two picks come from the SAME game, you cannot multiply them, because they are not independent.
Take a team to win and to score more than 20.5 points. Multiplying gives 57%. Priced together off the distribution of final scores, it is 66%. The naive number is wrong by nine points, because the same game script produces both outcomes.
Picks from the same game have to be priced together: some pairs reinforce each other, and some work against each other.
Parlays, answered
Are parlays always a bad idea?
They are a different bet from the one most people think they are making. Knowing the real probability is what lets you decide whether the payout is worth it.
Why is a same-game parlay different?
The legs are correlated. The same game script that produces one outcome often produces the other, so multiplying the two probabilities gives the wrong answer, sometimes badly wrong.
Learn the method
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