At present prices of bitcoin are too high compared to other altcoin coin. So when it goes down, it almost pulls the whole market down with it.
The price of Bitcoin remains the driving force of the cryto currency, rising and falling will affect other altcoins. So when a trader will trade, the most important thing is to pay attention and analyze the price of bitcoin, especially negative issues / positive issues or sentiments that can affect crypto prices as a whole.
Bitcoin effects will always affect other altcoins. Traders know about this so they cannot leave the analysis of bitcoin in altcoin trading.