The relationship between Altcoins and Bitcoin is not direct. If one altcoin's price increases that doesn't necessarily affect other altcoins or Bitcoin. BItcoin generally presents itself as the representative, being the first and at the top of the value chain.
I believe on the same thing. There are times that when Bitcoin is going strong some altcoins can be doing the same thing but there are also times when the opposite happened. In my view, the movement in altcoins depends on the factors that directly affected them individually and not collectively. Of course, this is quite related to the law of supply and demand and if one altcoin is doing all it can to make the project really look good and useful then I think the market can be reacting positively. Ascertaining the connection can be so difficult especially in the world of cryptocurrency where things can happen even for no reason at all.