diff --git a/src/brush/deap_api/nsga2.py b/src/brush/deap_api/nsga2.py
index a7d44f4d..a1a8c8b2 100644
--- a/src/brush/deap_api/nsga2.py
+++ b/src/brush/deap_api/nsga2.py
@@ -6,7 +6,7 @@
 
 def nsga2(toolbox, NGEN, MU, CXPB, use_batch, verbosity, rnd_flt):
     # NGEN = 250
-    # MU = 100
+    # MU   = 100
     # CXPB = 0.9
     # rnd_flt: random number generator to sample crossover prob
 
@@ -18,15 +18,18 @@ def calculate_statistics(ind):
 
     stats = tools.Statistics(calculate_statistics)
 
-    stats.register("ave", np.mean, axis=0)
+    stats.register("avg", np.mean, axis=0)
+    stats.register("med", np.median, axis=0)
     stats.register("std", np.std, axis=0)
     stats.register("min", np.min, axis=0)
     stats.register("max", np.max, axis=0)
 
     logbook = tools.Logbook()
-    logbook.header = "gen", "evals", "ave (O1 train, O2 train, O1 val, O2 val)", \
+    logbook.header = "gen", "evals", "avg (O1 train, O2 train, O1 val, O2 val)", \
+                                     "med (O1 train, O2 train, O1 val, O2 val)", \
                                      "std (O1 train, O2 train, O1 val, O2 val)", \
-                                     "min (O1 train, O2 train, O1 val, O2 val)"
+                                     "min (O1 train, O2 train, O1 val, O2 val)", \
+                                     "max (O1 train, O2 train, O1 val, O2 val)"
 
     pop = toolbox.population(n=MU)
 
@@ -68,14 +71,12 @@ def calculate_statistics(ind):
             if rnd_flt() < CXPB:
                 off1, off2 = toolbox.mate(ind1, ind2)
             else:
-                off1, off2 = ind1, ind2
-                
+                off1 = toolbox.mutate(off1)
+                off2 = toolbox.mutate(off2)
+            
             # avoid inserting empty solutions
-            if off1 != None: off1 = toolbox.mutate(off1)
-            if off1 != None: offspring.extend([off1])
-
-            if off2 != None: off2 = toolbox.mutate(off2)
-            if off2 != None: offspring.extend([off2])
+            if off1 is not None: offspring.extend([off1])
+            if off2 is not None: offspring.extend([off2])
 
         # archive.update(offspring)
         # Evaluate the individuals with an invalid fitness