Strategy Masterclass Part 2: Mean Reversion — RSI, Bollinger Bands & Stochastic Systems

📚 This is Part 2 of the Trading Strategy Masterclass series.

What is Mean Reversion?

Mean reversion is based on the statistical principle that prices tend to return to their average over time. When price stretches too far from its mean (average), it tends to "snap back" like a rubber band.

"What goes up too fast must come down. What falls too far must bounce."

This is the opposite philosophy to trend following — instead of riding trends, you bet against extreme moves.

Strategy 1: RSI Mean Reversion

Concept

The RSI (Relative Strength Index) measures the speed and magnitude of recent price changes on a scale of 0-100. Traditional levels:

• Above 70 = Overbought (price may fall)
• Below 30 = Oversold (price may rise)

Basic RSI Reversion Rules

Advanced: RSI with Trend Filter

Don't trade RSI blindly — add a trend filter:

1. Calculate 200 EMA as the trend direction
2. Price above 200 EMA: Only take RSI oversold signals (buy dips in uptrend)
3. Price below 200 EMA: Only take RSI overbought signals (sell rallies in downtrend)

This single filter can dramatically increase your win rate.

RSI Period Variations

Connors RSI (Professional Variant)

Larry Connors popularized the RSI(2) strategy specifically for stocks:

• Use RSI(2) instead of RSI(14)
• Buy when RSI(2) < 10, Sell when RSI(2) > 90
• Only trade in the direction of the 200 SMA
• Historically shows win rates above 70% on indices

Strategy 2: Bollinger Bands Reversion

Concept

Bollinger Bands consist of:

• Middle Band: 20-period SMA
• Upper Band: Middle + 2 standard deviations
• Lower Band: Middle - 2 standard deviations

Statistically, ~95% of price action should occur within the bands. When price touches or crosses a band, it's "stretched" and likely to revert.

Rules

Bollinger Band Squeeze (Volatility Breakout Setup)

When the bands contract tightly (squeeze), it signals low volatility — a big move is coming:

1. Identify the squeeze (bands narrower than recent history)
2. Wait for bands to expand
3. Trade in the direction of the breakout
4. Use the opposite band as your stop

Note: The squeeze setup is actually a breakout strategy, not mean reversion. Covered in Part 3.

Double Bollinger Bands (Advanced)

Use TWO sets of Bollinger Bands for more precise zones:

• Inner Bands: 20 SMA ± 1 Std Dev (the "buy/sell zone")
• Outer Bands: 20 SMA ± 2 Std Dev (the "extreme zone")

Zones:

• Between inner and outer bands = trending, stay with trend
• Beyond outer bands = extreme, expect reversion
• Between inner bands = neutral zone, no trade

Strategy 3: Stochastic Oscillator Reversion

Concept

The Stochastic Oscillator compares current price to its range over a period. It has two lines (%K and %D) oscillating between 0-100.

Rules

Stochastic + RSI Combo

For higher quality signals, require BOTH indicators to agree:

When both oscillators signal oversold/overbought simultaneously, the probability of a reversal is significantly higher.

Strategy 4: Statistical Mean Reversion (Z-Score)

Concept

For the more mathematically inclined, you can use the Z-Score to measure how many standard deviations price is from its mean.

Formula

Z-Score = (Price - SMA) / Standard Deviation

Rules

• Z-Score > +2.0: Price is 2 standard deviations above mean → Sell signal
• Z-Score < -2.0: Price is 2 standard deviations below mean → Buy signal
• Z-Score near 0: Price is at its mean → No action

Implementation

1. Calculate 20-period SMA
2. Calculate 20-period Standard Deviation
3. Compute Z-Score each bar
4. Trade when Z-Score exceeds ±2.0
5. Exit when Z-Score returns to ±0.5

When Mean Reversion Fails

Mean reversion strategies fail during strong trends:

• In a strong uptrend, price can stay "overbought" for extended periods
• RSI above 70 in a bull run is NOT a sell signal — it's a sign of strength
• Bollinger Band walks (price riding the upper/lower band) destroy reversion traders

Warning Signs:

• ADX > 30 (strong trend in place)
• Price consistently closing outside Bollinger Bands
• RSI stuck above 60 or below 40 for many bars

Solution: Switch to trend following strategies (Part 1) when ADX indicates a strong trend.

Summary

📙 Next: Part 3: Breakout & Momentum Strategies →
📘 Previous: Part 1: Trend Following
📚 Series Home: Trading Strategy Masterclass