usually the altcoin price will rise when the price of bitcoin rises and the price of the altcoin will drop when the price of bitcoin falls. to take advantage of price differences in the market to seek profit so that the price of the altcoin will rise and of course the price of bitcoin and altcoin is movement always giving the same price movement
I guess it is the common mistake or misconception about the altcoin's price. Altcoin is for alternative to bitcoin since bitcoin has the highest value among all of the cryptocurrency but it does not necessary affected by the bitcoin's price just so happen that investor and trader always panic sell whenever bitcoin's price goes down.