I've seen people try that and I've noticed the correlation myself. Around the end of last year (November/December 2017) it was possible to watch BTC jump 5-10% and jump over to ETH and catch the same wave 5-10 minutes later.

The problem is those patterns quickly disappear as automated trading picks them up. The window goes from 5-10 minutes to seconds or less. Much harder to act in such a small window.

The degree of coupling between assets is called "beta" - typically you're trying to reduce the coupling of one asset to another in your portfolio (explanation [1]) but you can definitely work the other way to make predictions.

I'm not sure what the technical term is for a time-lag correlation though, since that's what you're really after; it's not an interesting correlation for your model if you don't have time to trade ETH on the BTC signal.

[1]: https://www.quantopian.com/lectures/beta-hedging

All of these alt coins are tied to just few pairs (mostly BTC or ETH). When I was looking at the relationships in different instances (just eye balling, no statistical analysis), it seems that some the coins are just more or less volatile.