RSI measures a market's internal strength, by dividing the sum of up day
closing prices by the sum of down day closing prices over a specific
period of time. It returns a value within the range of 0 to 100. The classic
way to interpret RSI is to look for oversold levels below 30 and overbought
levels above 70. If underlying prices make a new high or low that isn't
confirmed by the RSI, this divergence can signal a price reversal.