What To Trust In Small Sample Size Theater
It’s an annual rite of November. With only around 10 games played by each team, it seems that there’s just enough data to start coming to conclusions based on this data. But all stats are not created equal; some numbers from the first 10 games can be trusted and others cannot.
I dug into data from NBA.com, looking at how a team did in a few different metrics in the first ten games of the season compared to how they did in them over the whole season.
The clearest thing here is that shot selection is incredibly consistent while shot making ability isn’t. The number of corner three attempts a team takes per game will regress to the mean only ~15% after 10 games, while how a team shoots from the corner over the first 10 games is over 55% luck. This also gives a bit of a proxy for which shots are the most high variance. Three pointers from both spots on the floor have huge luck components over the first 10 games, but field goal percentage in the restricted area over the first 10 can be a bit more representative of the team’s actual ability.
More luck is involved in defensive rebounding percentage and defensive rating than in offensive rebounding percentage and offensive rating. This may indicate that a team can better control their own offensive performance than control an opponent’s offensive performance. Good offense beats good defense (Or, bad offense is worse than bad defense).
A team’s pace is fairly real after 10 games, likely do to the fact that pace is about play style, not results.
There are conclusions that can be drawn from the first ten games of a season, but it’s tough to use the first ten games to help predict the entire season. Excluding shot selection statistics and pace, every stat tested above was over 25% luck in the first 10 games of the season. This is a far cry from saying that statistics from the first 10 games mean nothing, though. They tell what has happened, and those numbers are important in analyzing the season so far. Their predictive ability is what’s lacking.