Updated stats docs
Changed definition of alpha factor from efficiencies to exposures
@@ -30,8 +30,8 @@ Variable Definition
``mu_off`` Total expected counts in the off region
``mu_sig`` Signal expected counts in the on region
``mu_bkg`` Background expected counts in the on region
-``a_on`` Relative background efficiency in the on region
-``a_off`` Relative background efficiency in the off region
+``a_on`` Relative background exposure in the on region
+``a_off`` Relative background exposure in the off region
``alpha`` Background efficiency ratio ``a_on`` / ``a_off``
``n_bkg`` Background estimate in the on region
================= ====================================================
