Ensemble: Mage: Fix iterative mean computation.

src/Solver/Mage.py

@@ -1638,8 +1638,9 @@ class Mage8(Mage):
             res["traces"] = []
         else:
             # Get mean results for Z and Q
-            res["z_mean"] = (res["z_mean"] + z) / 2
-            res["q_mean"] = (res["q_mean"] + q) / 2
+            n = run_number
+            res["z_mean"] = (res["z_mean"] * n + z) / (n + 1)
+            res["q_mean"] = (res["q_mean"] * n + q) / (n + 1)
 
             # Z and Q min max values
             res["z_min"] = np.minimum(z, res["z_min"])