Fix rate of change calculation of statistics sensor (#32597)

* Fix rate of change of statistics sensor

* Fix test

tests/components/statistics/test_sensor.py

@@ -36,7 +36,7 @@ class TestStatisticsSensor(unittest.TestCase):
         self.variance = round(statistics.variance(self.values), 2)
         self.change = round(self.values[-1] - self.values[0], 2)
         self.average_change = round(self.change / (len(self.values) - 1), 2)
-        self.change_rate = round(self.average_change / (60 * (self.count - 1)), 2)
+        self.change_rate = round(self.change / (60 * (self.count - 1)), 2)
 
     def teardown_method(self, method):
         """Stop everything that was started."""