diff --git a/app/strategies/quant_algos/statistical_algos.py b/app/strategies/quant_algos/statistical_algos.py
index ac5c4a3..dce1b8d 100644
--- a/app/strategies/quant_algos/statistical_algos.py
+++ b/app/strategies/quant_algos/statistical_algos.py
@@ -11,20 +11,23 @@ def linear_regression_channel(
     """Deviation from linear regression line. Trade reversion to line."""
     if len(prices) < lookback:
         return 0.0, f"warming up ({len(prices)}/{lookback})"
-    x = list(range(lookback))
     y = prices[-lookback:]
-    n = len(x)
-    sx, sy = sum(x), sum(y)
-    sxx = sum(xi * xi for xi in x)
-    sxy = sum(xi * yi for xi, yi in zip(x, y))
+    n = lookback
+    sx = n * (n - 1) // 2
+    sxx = n * (n - 1) * (2 * n - 1) // 6
+    sy = sum(y)
+    sxy = sum(xi * yi for xi, yi in enumerate(y))
     den = n * sxx - sx * sx
     if den == 0:
         return 0.0, "singular"
     slope = (n * sxy - sx * sy) / den
     intercept = (sy - slope * sx) / n
     pred = intercept + slope * (n - 1)
-    residuals = [yi - (intercept + slope * xi) for xi, yi in zip(x, y)]
-    var = sum(r * r for r in residuals) / len(residuals)
+    residual_sum_sq = 0.0
+    for xi, yi in enumerate(y):
+        residual = yi - (intercept + slope * xi)
+        residual_sum_sq += residual * residual
+    var = residual_sum_sq / n
     std = math.sqrt(var) if var > 0 else 1e-10
     p = prices[-1]
     dev = (p - pred) / std if std else 0
diff --git a/shared/tests/test_statistical_algos.py b/shared/tests/test_statistical_algos.py
new file mode 100644
index 0000000..d1aea1d
--- /dev/null
+++ b/shared/tests/test_statistical_algos.py
@@ -0,0 +1,54 @@
+import math
+
+from app.strategies.quant_algos.statistical_algos import linear_regression_channel
+
+
+def _previous_linear_regression_channel(prices, lookback=20):
+    if len(prices) < lookback:
+        return 0.0, f"warming up ({len(prices)}/{lookback})"
+    x = list(range(lookback))
+    y = prices[-lookback:]
+    n = len(x)
+    sx, sy = sum(x), sum(y)
+    sxx = sum(xi * xi for xi in x)
+    sxy = sum(xi * yi for xi, yi in zip(x, y))
+    den = n * sxx - sx * sx
+    if den == 0:
+        return 0.0, "singular"
+    slope = (n * sxy - sx * sy) / den
+    intercept = (sy - slope * sx) / n
+    pred = intercept + slope * (n - 1)
+    residuals = [yi - (intercept + slope * xi) for xi, yi in zip(x, y)]
+    var = sum(r * r for r in residuals) / len(residuals)
+    std = math.sqrt(var) if var > 0 else 1e-10
+    p = prices[-1]
+    dev = (p - pred) / std if std else 0
+    sig = -dev
+    return max(-2, min(2, sig)), f"dev={dev:.2f} pred={pred:.2f}"
+
+
+def test_linear_regression_channel_matches_previous_outputs():
+    cases = [
+        [100 + i * 0.2 for i in range(80)],
+        [100 + math.sin(i / 3) * 2 + i * 0.03 for i in range(80)],
+        [120 - i * 0.35 + math.cos(i / 4) for i in range(80)],
+        [100, 102, 101, 103, 99, 98, 100, 101, 103, 104, 102, 101],
+    ]
+
+    for prices in cases:
+        expected_signal, expected_detail = _previous_linear_regression_channel(
+            prices, lookback=min(20, len(prices))
+        )
+        actual_signal, actual_detail = linear_regression_channel(
+            prices, lookback=min(20, len(prices))
+        )
+
+        assert actual_signal == expected_signal
+        assert actual_detail == expected_detail
+
+
+def test_linear_regression_channel_keeps_warmup_behavior():
+    assert linear_regression_channel([1.0, 2.0, 3.0], lookback=5) == (
+        0.0,
+        "warming up (3/5)",
+    )