Here are some interesting indicators over the past 15 years, using a one week interval.
On the chart I've used S5FI which tells us the number of stocks trading above their 50 day moving average (orange line). On it's own I might assume this could go either way. But then you look over at the indicator below, Overbought/Oversold and you'll see we'll likely have 2-3 more down weeks minimum. When used together S5FI and the overbought indicators are extremely accurate in telling me the depth of the sell-off. Below that, is the MACD or Moving average convergence/divergence and here it tells me we're just getting started on the sell-off. The RSI is trending down which strengthens a sell-off. The Fear & Greed indicator which is the last indicator tells me that this correction has a ways to go before fear signals the end of the sell-off.
As with anything, be smart, manage risk, use hard tight stops and don't expect the market to ever do what we want it to.
Cheers!