How much closing data do i need for accurate Correlation

[king_david599]

Guys I trade Correlation Hedge, but my Correlation result aren't the same as the big companies such as myfxbook, and oanda! Does that mean the amount of closing data I have I not enough! I use the closing data of 15 minutes, (because I trade 15m timeframe) and I use just the last 24 bars/candles.
Is this enough? And pls what do you guys think?Thanks.