$NDXのエントリーシグナルにVIXを使う？

I've definitely seen that play out. A sharp VIX spike often means a short-term bottom is near for equities. The challenge is distinguishing a dip from a sustained downturn.

Quantifying it is the tricky part. I usually just watch for a VIX close above its Bollinger Bands, combined with $NDX being significantly oversold on the RSI. Not perfect, but it helps.

While there's a general inverse correlation, I'd be cautious using VIX alone as a direct entry signal. VIX can stay elevated for extended periods, and sometimes the 'fear' is justified and more selling follows.