Slow stochastic oscillator

What the numbers mean

The same 14-bar range lookback, but %K is first smoothed by 3 periods (that second number is the fast %D promoted to become the slow %K), and the final %D is a further 3-period average. The extra smoothing is the only difference from the fast version.

• 14 — the range lookback
• 3 — the smoothing that turns fast %D into slow %K
• 3 — the final %D signal-line average
• 21, 5, 5 — a slower variant with fewer false crossings
• 80 / 20 — the standard extremes

How it is used

The standard form for most traders: readings above 80 and below 20 mark stretched conditions, and %K crossing %D from an extreme is the conventional signal — best used when price is oscillating in a range rather than trending.

• %K crossing %D below 20 → buy trigger in a range
• %K crossing %D above 80 → sell trigger in a range
• Both lines climbing out of oversold together → a turn with some conviction behind it

How it relates to everything else

The slow stochastic is the version most traders actually use, and it pairs naturally with RSI because the two measure different things — RSI compares the size of gains to losses, the stochastic compares the close to the bar range. When both reach an extreme at once, the reading is treated as much stronger than either alone.

• Stochastic + RSI both oversold → two independent measures agreeing
• Stochastic + ADX below 20 → the environment these signals are designed for
• In a strong trend it pins at an extreme; a 200-SMA filter keeps you on the right side

What to watch for

It still pins at extremes in a strong trend. Raising the lookback to 21 reduces false crossings but pushes the signals later.