In trading on Tuesday, shares of the Proshares UltraShort Nasdaq Biotechnology ETF (BIS) entered into oversold territory, changing hands as low as $43.97 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 Proshares UltraShort Nasdaq Biotechnology, the RSI reading has hit 29.4 — by comparison, the RSI reading for the S&P 500 is currently 54.6. A bullish investor could look at BIS's 29.4 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), BIS's low point in its 52 week range is $42.32 per share, with $101.68 as the 52 week high point — that compares with a last trade of $43.97. Proshares UltraShort Nasdaq Biotechnology shares are currently trading off about 1.2% on the day.