diff --git a/code/enums.py b/code/enums.py
index 7abeb4e..144d24e 100644
--- a/code/enums.py
+++ b/code/enums.py
@@ -95,7 +95,7 @@ class Dimension():
     }
 
     # outlider factor
-    IQR_FACTOR = 3
+    ALPHA = 0.1
 
     _filter_thresholds = {
         PM2_5: (0, 999)
diff --git a/code/routers/city.py b/code/routers/city.py
index dbce015..10510c6 100644
--- a/code/routers/city.py
+++ b/code/routers/city.py
@@ -91,12 +91,9 @@ async def get_average_measurements_by_city(
     data = []
     for dim, val_list, val_count, s_cnt in q.all():
         a = np.array(val_list)
-        q1 = np.percentile(a, 25)
-        q3 = np.percentile(a, 75)
-        iqr = (q3 - q1)
 
-        l = q1 - iqr * Dimension.IQR_FACTOR
-        r = q3 + iqr * Dimension.IQR_FACTOR
+        l = np.percentile(a, 100 * (Dimension.ALPHA / 2))
+        r = np.percentile(a, 100 * (1 - (Dimension.ALPHA / 2)))
 
         b = a[(a >= l) & (a <= r)]