Explainer

What the prediction ranges mean

Every prediction carries a range, and the result should land inside it 80% of the time: one night in ten below it, one night in ten above it. You won't see the range printed next to the prediction; it's what turns a prediction and a bookmaker line into a probability, and the track record shows whether it holds.

An example

Say a player is predicted for 22.4 points with a range of 15 to 30. That doesn't mean 22.4 is likely to the decimal; it means that across nights like tonight, he scores between 15 and 30 about eight times in ten, under 15 about once, and over 30 about once.

Why ranges are lopsided

A player can't score fewer than zero points, but he can have a career night. So ranges stretch further above the prediction than below it, especially for rebounds, assists and threes, where totals are small. A threes prediction of 1.4 might have a range of 0 to 3.

Combined markets

For points + rebounds + assists and the other combined markets, we don't just add three ranges together. On nights a player scores more he also tends to play more and pick up more rebounds and assists, so the parts move together. Combined ranges are fitted on players' actual combined totals: on games held out for testing they held 80% of results. Treating the parts as independent would have held only 73% to 78%.

Wider when we know less

Players with only a handful of NBA games get wider ranges, because there's less to go on. Early in the season the ranges also carry more of last season's evidence.

How the range becomes an edge

The range and the edge come from the same distribution. A line near the middle of the range is close to a coin flip on our numbers; a line near either end means one side lands far more often than the other. The edge on the board turns that into a probability and compares it with the bookmaker's price, so you never have to eyeball a range yourself.

Checking the ranges are honest

If the ranges were too narrow, results would fall outside them more than one night in five; too wide, less. The track record shows how often results actually landed inside the range this season, market by market, and how the misses split above and below. That page is updated every morning, and nothing is removed after the fact.