diff --git a/.github/workflows/limit-size.yml b/.github/workflows/limit-size.yml
new file mode 100644
index 0000000..be15436
--- /dev/null
+++ b/.github/workflows/limit-size.yml
@@ -0,0 +1,16 @@
+name: Limit complexity
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Install lizard
+      run: pip install lizard
+
+    - name: Limit complexity
+      run: $HOME/.local/bin/lizard --CCN 3
\ No newline at end of file
diff --git a/__pycache__/alerts.cpython-38.pyc b/__pycache__/alerts.cpython-38.pyc
new file mode 100644
index 0000000..5c988ca
Binary files /dev/null and b/__pycache__/alerts.cpython-38.pyc differ
diff --git a/__pycache__/statistics.cpython-38.pyc b/__pycache__/statistics.cpython-38.pyc
new file mode 100644
index 0000000..209607b
Binary files /dev/null and b/__pycache__/statistics.cpython-38.pyc differ
diff --git a/alerts.py b/alerts.py
new file mode 100644
index 0000000..6ba8d67
--- /dev/null
+++ b/alerts.py
@@ -0,0 +1,31 @@
+import statistics
+
+# below: alerts tests
+
+class EmailAlert:
+
+  def __init__(self):
+    self.emailSent = False # by default
+
+class LEDAlert:
+
+  def __init__(self):
+    self.ledGlows = False # by default
+
+class StatsAlerter:
+
+  def __init__(self, maxThresh, alertArrs):
+
+    self.maxThresh = maxThresh
+    self.alertArrs = alertArrs
+    self.emailAlert = self.alertArrs[0]
+    self.ledAlert = self.alertArrs[1]
+
+  def checkAndAlert(self, numbers):
+
+    stats = statistics.calculateStats(numbers)
+
+    if stats["max"] > self.maxThresh:
+
+      self.emailAlert.emailSent = True
+      self.ledAlert.ledGlows = True
\ No newline at end of file
diff --git a/statistics.py b/statistics.py
index fda1724..fe03d04 100644
--- a/statistics.py
+++ b/statistics.py
@@ -1,3 +1,18 @@
+import math
+from turtle import st
 
 def calculateStats(numbers):
-  return None
+
+  stats = dict(zip(["avg", "max", "min"], [math.nan, math.nan, math.nan]))
+
+  if type(numbers) != list: 
+
+    return None
+    
+  if len(numbers) != 0:
+
+    stats["avg"] = round((sum(numbers) / len(numbers)), 3)
+    stats["max"] = max(numbers)
+    stats["min"] = min(numbers) # min_max_report test 
+  
+  return stats
\ No newline at end of file
diff --git a/statistics.test.py b/statistics.test.py
index cb914d6..6babe61 100644
--- a/statistics.test.py
+++ b/statistics.test.py
@@ -1,5 +1,7 @@
+from cmath import isnan
 import unittest
 import statistics
+import alerts
 
 class StatsTest(unittest.TestCase):
   def test_report_min_max_avg(self):
@@ -15,12 +17,20 @@ def test_avg_is_nan_for_empty_input(self):
     # nan (not-a-number), as defined in the math package
     # Design the assert here.
     # Use nan and isnan in https://docs.python.org/3/library/math.html
+    self.assertTrue(isnan(computedStats["avg"]))
+    self.assertTrue(isnan(computedStats["max"]))
+    self.assertTrue(isnan(computedStats["min"]))
+
+  def test_invalid_arg_returns_None(self):
+    # tests if calculateStats returns None on receiving non-array argument for 'numbers'
+    computedStats = statistics.calculateStats("a string")
+    self.assertTrue((computedStats == None), None)
 
   def test_raise_alerts_when_max_above_threshold(self):
-    emailAlert = EmailAlert()
-    ledAlert = LEDAlert()
+    emailAlert = alerts.EmailAlert() # added statistics module identifier for class instantiation
+    ledAlert = alerts.LEDAlert()
     maxThreshold = 10.5
-    statsAlerter = StatsAlerter(maxThreshold, [emailAlert, ledAlert])
+    statsAlerter = alerts.StatsAlerter(maxThreshold, [emailAlert, ledAlert])
     statsAlerter.checkAndAlert([22.6, 12.5, 3.7])
     self.assertTrue(emailAlert.emailSent)
     self.assertTrue(ledAlert.ledGlows)