It's obvious, just look at all the trading pair, is btc/altcoin so whatever btc price movement is, every altcoin is going to be affected and we've seen this relationship for so many years now that it's safe to conclude that they have.

But there could be some who argue that it's not, that altcoin has it's own price movement. Maybe a tiny percentage though, specially those meme and shit coins who are being used for price manipulations, i.e. pump and dump scheme.