Rounds
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Avg error
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Best avg (saved)
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Look at the scatterplot and guess its correlation coefficient (r). It's the fastest way to actually feel what r = 0.3 vs 0.8 looks like.
The Pearson correlation coefficient r measures the strength and direction of a linear relationship between two variables, on a scale from −1 to +1. r = +1 is a perfect upward line, r = −1 a perfect downward line, and r = 0 means no linear relationship. The tighter the points cluster around a straight line, the closer |r| is to 1.
Most people can recite "r ranges from −1 to 1" but have no visual sense of what r = 0.5 actually looks like — it's far messier than beginners expect. Repeatedly guessing and getting the answer builds fast, durable intuition, which makes you much better at sanity-checking real analyses. A scatterplot that "looks strong" is often only r ≈ 0.6.
No — correlation is not causation. A strong r tells you two variables move together, not that one causes the other; a lurking third variable or coincidence can produce it. See correlation vs causation.
Each round generates a fresh cloud of points around a random target strength, then computes the actual Pearson r of those exact points — that computed value is what you're scored against. To get r for your own data, use the correlation calculator.