hausman performs Hausman's specification test.  To use hausman, perform the following steps.

      (1) obtain an estimator that is consistent whether or not the hypothesis is true;
      (2) store the estimation results under name-consistent by using estimates store;
      (3) obtain an estimator that is efficient (and consistent) under the hypothesis that you are testing,
          but inconsistent otherwise;
      (4) store the estimation results under name-efficient by using estimates store;
      (5) use hausman to perform the test