diff --git a/interactive.py b/interactive.py
index 2c9858b..e3c3cee 100644
--- a/interactive.py
+++ b/interactive.py
@@ -59,7 +59,7 @@ class Moulder(FigureCanvasQTAgg):
 
         # Set arbitrary density and error values (only for first implementations)
         # It will be determined by sliders/entries in MoulderApp
-        self._density = 100
+        self._density = 0
         self._error = 0
 
         # Data min and max (only for first implementations)
@@ -114,7 +114,7 @@ class Moulder(FigureCanvasQTAgg):
     def predicted(self):
         self._predicted = talwani.gz(self.x, self.z, self.model)
         if self.error > 0:
-            self._predicted = utils.contaminate(self.predicted, self.error)
+            self._predicted = utils.contaminate(self._predicted, self.error)
         return self._predicted
 
     @property
diff --git a/moulder.py b/moulder.py
index e3fdb30..8b24f4e 100644
--- a/moulder.py
+++ b/moulder.py
@@ -120,13 +120,13 @@ class MoulderApp(QMainWindow):
 
         self.error_slider = QSlider(Qt.Horizontal)
         self.error_slider.setMinimum(0)
-        self.error_slider.setMaximum(100)
+        self.error_slider.setMaximum(5)
         self.error_slider.setValue(0)
-        self.error_slider.setTickInterval(10)
+        self.error_slider.setTickInterval(0.5)
         self.error_slider.setTickPosition(QSlider.TicksBelow)
         self.error_spinbox = QDoubleSpinBox()
         self.error_spinbox.setMinimum(0)
-        self.error_spinbox.setMaximum(100)
+        self.error_spinbox.setMaximum(5)
         self.error_spinbox.setValue(0)
         self.error_spinbox.setSingleStep(0.1)