PSI blurb in Docs for 0.8.3

docs/source/profiler.rst

@@ -146,6 +146,12 @@ between them. Create the difference report like this:
     diff_report = profile1.diff(profile2)
     print(diff_report)
 
+The `.diff()` operation is available between two profiles, although there are different
+outputs depending on the type of profile being differenced. For example, for numerical
+column profiles (e.g. integers and floats), two valuable calculations that 
+`.diff()` returns are `t-test` and `psi` (Popoulation Stability Index) 
+for understanding distributional changes.
+
 The difference report contains a dictionary that mirrors the profile report. 
 Each data type has its own difference:
 
@@ -208,6 +214,7 @@ Below is the structured difference report:
                                      'p-value': float},
                     'welch': {'df': float,
                               'p-value': float}},
+                'psi': float,
                 "chi2-test": {
                     "chi2-statistic": float,
                     "df": int,