diff --git a/document/FlashcardDocumentSampler.py b/document/FlashcardDocumentSampler.py
index 8a8d872..3cdf9d1 100644
--- a/document/FlashcardDocumentSampler.py
+++ b/document/FlashcardDocumentSampler.py
@@ -9,6 +9,6 @@ class FlashcardDocumentSampler(document.AbstractDocumentSampler):
   def sample_document(self):
     doc_features = {}
     doc_features['doc_id'] = self._doc_count
-    doc_features['difficulty'] = self._rng.random_sample((1, 3))
+    doc_features['difficulty'] = self._rng.uniform(0, 5, (1, 3))
     self._doc_count += 1
     return self._doc_ctor(**doc_features)
\ No newline at end of file
diff --git a/user/FlashcardUserModel.py b/user/FlashcardUserModel.py
index 306598a..0ef3e06 100644
--- a/user/FlashcardUserModel.py
+++ b/user/FlashcardUserModel.py
@@ -52,7 +52,7 @@ class FlashcardUserModel(user.AbstractUserModel):
     doc_id = doc._doc_id
     W = self._user_state._W[doc_id]
     if not W.any(): # uninitialzed
-      self._user_state._W[doc_id] = W = doc.base_difficulty + np.random.uniform(-0.5, 0.5, (1, 3)) # a uniform error for each user
+      self._user_state._W[doc_id] = W = doc.base_difficulty * np.random.uniform(0.5, 2.0, (1, 3)) # a uniform error for each user
       print(W)
     # use exponential function to simulate whether the user recalls
     last_review = self._user_state._time - self._user_state._last_review[doc_id]