diff --git a/ocw/metrics.py b/ocw/metrics.py
index fb7bce34..ee5c1f9e 100644
--- a/ocw/metrics.py
+++ b/ocw/metrics.py
@@ -184,8 +184,9 @@ def run(self, reference_dataset, target_dataset):
         .. note::
            Overrides BinaryMetric.run()
 
-        :param ref_dataset: The reference dataset to use in this metric run
-        :type ref_dataset: ocw.dataset.Dataset object
+        :param reference_dataset: The reference dataset to use in this metric
+            run
+        :type reference_dataset: ocw.dataset.Dataset object
         :param target_dataset: The target dataset to evaluate against the
             reference dataset in this metric run
         :type target_dataset: ocw.dataset.Dataset object
@@ -201,22 +202,23 @@ class RMSError(BinaryMetric):
     '''Calculate the Root Mean Square Difference (RMS Error), with the mean
        calculated over time and space.'''
 
-    def run(self, eval_dataset, ref_dataset):
+    def run(self, reference_dataset, target_dataset):
         '''Calculate the Root Mean Square Difference (RMS Error), with the mean
            calculated over time and space.
 
         .. note::
            Overrides BinaryMetric.run()
 
-        :param eval_dataset: The dataset to evaluate against the reference
-            dataset
-        :type eval_dataset: ocw.dataset.Dataset object
-        :param ref_dataset: The reference dataset for the metric
+        :param reference_dataset: The reference dataset to use in this metric
+            run
+        :type reference_dataset: ocw.dataset.Dataset object
+        :param target_dataset: The target dataset to evaluate against the
+            reference dataset in this metric run
         :type target_dataset: ocw.dataset.Dataset object
 
         :returns: The RMS error, with the mean calculated over time and space
         '''
 
-        sqdiff = (eval_dataset.values - ref_dataset.values) ** 2
+        sqdiff = (reference_dataset.values - target_dataset.values) ** 2
         return numpy.sqrt(sqdiff.mean())
 
diff --git a/ocw/tests/test_metrics.py b/ocw/tests/test_metrics.py
index a2ca025c..affb9376 100644
--- a/ocw/tests/test_metrics.py
+++ b/ocw/tests/test_metrics.py
@@ -202,27 +202,27 @@ class TestRMSError(unittest.TestCase):
     def setUp(self):
         # Set metric.
         self.metric = metrics.RMSError()
-        # Initialize evaluation dataset.
-        self.eval_lats = np.array([10, 20, 30, 40, 50])
-        self.eval_lons = np.array([5, 15, 25, 35, 45])
-        self.eval_times = np.array([dt.datetime(2000, x, 1)
-                                    for x in range(1, 13)])
-        self.eval_values = np.array([4] * 300).reshape(12, 5, 5)
-        self.eval_variable = "eval"
-        self.eval_dataset = Dataset(self.eval_lats, self.eval_lons,
-            self.eval_times, self.eval_values, self.eval_variable)
         # Initialize reference dataset.
         self.ref_lats = np.array([10, 20, 30, 40, 50])
         self.ref_lons = np.array([5, 15, 25, 35, 45])
         self.ref_times = np.array([dt.datetime(2000, x, 1)
                                    for x in range(1, 13)])
-        self.ref_values = np.array([2] * 300).reshape(12, 5, 5)
+        self.ref_values = np.array([4] * 300).reshape(12, 5, 5)
         self.ref_variable = "ref"
         self.ref_dataset = Dataset(self.ref_lats, self.ref_lons,
             self.ref_times, self.ref_values, self.ref_variable)
+        # Initialize target dataset.
+        self.tgt_lats = np.array([10, 20, 30, 40, 50])
+        self.tgt_lons = np.array([5, 15, 25, 35, 45])
+        self.tgt_times = np.array([dt.datetime(2000, x, 1)
+                                    for x in range(1, 13)])
+        self.tgt_values = np.array([2] * 300).reshape(12, 5, 5)
+        self.tgt_variable = "tgt"
+        self.tgt_dataset = Dataset(self.tgt_lats, self.tgt_lons,
+            self.tgt_times, self.tgt_values, self.tgt_variable)
 
     def test_function_run(self):
-        result = self.metric.run(self.eval_dataset, self.ref_dataset)
+        result = self.metric.run(self.ref_dataset, self.tgt_dataset)
         self.assertEqual(result, 2.0)