There is definitely a relationship between the price of bitcoin and altcoins. Altcoins drop as bitcoin moves harder. In fact, whether the bitcoin rises or falls, the first reaction of altcoins is falling. After Bitcoin is fixed and stays stable, altcoins start to increase.
I would better say, they were correlated for a very long time. Meanwhile, look at the cryptocurrencies market now. When Bitcoin is going up, most altcoins are sliding down. Some alts manage to jump very high from time to time. Nevertheless, they do not stay on the top for long.
Bitcoin moves altcoins will move as well either to go up or going down so that can be a good correlation between these two. Any market can’t stay on the top for a long time because they have to go down as well, there’s no fixed price in the market everything has to move and the volatility of the market is getting higher every year.