What correlation means
Correlation ranges from −1 to 1. A value near 1 means two coins move up and down together almost every day; near 0 means their daily moves are unrelated. We calculate it on daily returns over a rolling 60-day window.
Why it matters for diversification
Most large altcoins are highly correlated with Bitcoin, so owning several of them does not diversify as much as people think. Periods when correlation drops show coins moving on their own news.