diff --git a/experiment_utils/experiment_analyzer.py b/experiment_utils/experiment_analyzer.py
index 05498ca..bb3593d 100644
--- a/experiment_utils/experiment_analyzer.py
+++ b/experiment_utils/experiment_analyzer.py
@@ -183,7 +183,7 @@ def __create_formula(self, outcome_variable, type: str = 'regression'):
 
         if len(reg_covs) > 0:
             zreg_covs = [f"z_{cov}" for cov in reg_covs]
-            formula = formula_dict[type] + ' + '.join(zreg_covs)
+            formula = formula_dict[type] +  ' + ' + ' + '.join(zreg_covs)
         else:
             formula = formula_dict[type]