In trading on Thursday, shares of the First Trust ISE Global Wind Energy Index Fund ETF (FAN) entered into oversold territory, changing hands as low as $12.07 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of First Trust ISE Global Wind Energy Index Fund, the RSI reading has hit 29.0 — by comparison, the RSI reading for the S&P 500 is currently 32.2. A bullish investor could look at FAN's 29.0 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), FAN's low point in its 52 week range is $9.51 per share, with $13.60 as the 52 week high point — that compares with a last trade of $12.12. First Trust ISE Global Wind Energy Index Fund shares are currently trading down about 0.9% on the day.