diff --git a/src/propeller/gp.cljc b/src/propeller/gp.cljc
index bc1d990..9df6d01 100644
--- a/src/propeller/gp.cljc
+++ b/src/propeller/gp.cljc
@@ -11,40 +11,8 @@
             [propeller.push.instructions.numeric]
             [propeller.push.instructions.polymorphic]
             [propeller.push.instructions.string]
-            [propeller.push.instructions.vector]))
-
-(defn mean [coll]
-  (let [sum (apply + coll)
-        count (count coll)]
-    (if (pos? count)
-      (/ sum (float count))
-      0)))
-
-(defn median [coll]
-  (let [sorted (sort coll)
-        cnt (count sorted)
-        halfway (quot cnt 2.0)]
-    (if (odd? cnt)
-      (nth sorted halfway)
-      (let [bottom (dec halfway)
-            bottom-val (nth sorted bottom)
-            top-val (nth sorted halfway)]
-        (mean [bottom-val top-val])))))
-
-(defn median-absolute-deviation
-  [coll]
-  (let [median-val (median coll)]
-    (median (map #(Math/abs (- % median-val)) coll))))
-
-(defn epsilon-list
-  "Calculates the median absolute deviation of the population."
-  [pop]
-  (let [error-list (map :errors pop)
-        length (count (:errors (first pop)))]
-    (loop [epsilons [] i 0]
-      (if (= i length)
-        epsilons
-        (recur (conj epsilons (median-absolute-deviation (map #(nth % i) error-list))) (inc i))))))
+            [propeller.push.instructions.vector]
+            [propeller.selection :as selection]))
 
 (defn report
   "Reports information each generation."
@@ -85,7 +53,7 @@
                                    population))
           best-individual (first evaluated-pop)
           argmap (if (= (:parent-selection argmap) :epsilon-lexicase)
-                           (assoc argmap :epsilons (epsilon-list evaluated-pop))
+                           (assoc argmap :epsilons (selection/epsilon-list evaluated-pop))
                            argmap)]
       (if (:custom-report argmap)
         ((:custom-report argmap) evaluated-pop generation argmap)
diff --git a/src/propeller/selection.cljc b/src/propeller/selection.cljc
index 2ab96d9..f6b2932 100755
--- a/src/propeller/selection.cljc
+++ b/src/propeller/selection.cljc
@@ -1,4 +1,5 @@
-(ns propeller.selection)
+(ns propeller.selection
+  (:require [propeller.tools.math :as math-tools]))
 
 (defn tournament-selection
   "Selects an individual from the population using a tournament."
@@ -21,6 +22,15 @@
                        survivors)
                (rest cases))))))
 
+(defn epsilon-list
+  [pop]
+  (let [error-list (map :errors pop)
+        length (count (:errors (first pop)))]
+    (loop [epsilons [] i 0]
+      (if (= i length)
+        epsilons
+        (recur (conj epsilons (math-tools/median-absolute-deviation (map #(nth % i) error-list))) (inc i))))))
+
 (defn epsilon-lexicase-selection
   "Selects an individual from the population using epsilon-lexicase selection."
   [pop argmap]
diff --git a/src/propeller/tools/math.cljc b/src/propeller/tools/math.cljc
index 03ed549..574dd18 100755
--- a/src/propeller/tools/math.cljc
+++ b/src/propeller/tools/math.cljc
@@ -6,6 +6,29 @@
 (defonce E #?(:clj  Math/E
               :cljs js/Math.PI))
 
+(defn mean [coll]
+  (let [sum (apply + coll)
+        count (count coll)]
+    (if (pos? count)
+      (/ sum (float count))
+      0)))
+
+(defn median [coll]
+  (let [sorted (sort coll)
+        cnt (count sorted)
+        halfway (quot cnt 2.0)]
+    (if (odd? cnt)
+      (nth sorted halfway)
+      (let [bottom (dec halfway)
+            bottom-val (nth sorted bottom)
+            top-val (nth sorted halfway)]
+        (mean [bottom-val top-val])))))
+
+(defn median-absolute-deviation
+  [coll]
+  (let [median-val (median coll)]
+    (median (map #(Math/abs (- % median-val)) coll))))
+
 (defn abs
   "Returns the absolute value of a number."
   [x]
diff --git a/test/propeller/tools/math_test.cljc b/test/propeller/tools/math_test.cljc
index c189536..541fb9a 100644
--- a/test/propeller/tools/math_test.cljc
+++ b/test/propeller/tools/math_test.cljc
@@ -60,4 +60,16 @@
       (t/is (m/approx= (m/tan (/  m/PI 4)) 1.0 0.00001))
       (t/is (= (m/tan 0) 0.0)))
 
+(t/deftest mean-test
+  (t/is (= (m/mean []) 0.0))
+  (t/is (= (m/mean [1 2 3 4 5]) 3.0))
+  (t/is (= (m/mean '(6 7 8 9 10)) 8.0) 8.0))
+
+(t/deftest median-test
+  (t/is (= (m/median [1 2 3 4 5]) 3))
+  (t/is (= (m/median '(1 2 3 4 5 6)) 3.5)))
+
+(t/deftest median-absolute-deviation-test
+  (t/is (= (m/median-absolute-deviation [1 2 3 4 5]) 1))
+  (t/is (= (m/median-absolute-deviation '(1 2 3 4 5 6)) 1.5)))