With a pullback led by QQQ and the high flyers, several ETFs have become short-term oversold in a longer term uptrend. In Dow Theory terms, the primary trend for these ETFs is up and the secondary trend is down. A secondary downtrend within a primary uptrend is considered a correction within that uptrend and a possible opportunity.
Corrections, however, are like a box of chocolates, the Forrest Gump ones. You never know what you are going to get. Some corrections are short and sweet, some are more drawn out and some result in bigger trend reversals. The idea is that the odds favor an upside resolution at some point because the bigger trend (up) is the dominant force at work. Trading and investing is all about probabilities. There are NO certainties.
The chart below shows the Biotech ETF (IBB) hitting a new high in February and falling back to the 157 area the last three weeks. The long-term trend is up because price is above the rising 200-day and StochClose triggered bullish in early November with a move above 60 (green arrow). This indicator is part of the TrendInvestorPro Indicator Edge Plugin for StockCharts ACP. 
The middle window shows RSI(14) dipping below 40 and becoming modestly oversold (yellow circle). Overall, I use the 30-50 zone to identify ETFs with varying degrees of oversold conditions. Thus, IBB is oversold within a long-term uptrend and a falling wedge of sorts is taking shape on the price chart. A break above the red resistance line would reverse this short-term downtrend and signal a resumption of the bigger uptrend.
The table below tracks trend signals (StochClose) and short-term oversold conditions for 120 ETFs in the Core List at TrendInvestorPro.com. We can see that two ARK ETFs are quite oversold, two cybersecurity ETFs and a clean energy ETF. Check out the charts and do your own due diligence. Click here to subscribe  and get immediate access to our ETF Trends, Patterns & Setups report, Broad Market Timing Strategies and Weekend Video.