diff --git a/src/DataFrame/Operations/Aggregation.hs b/src/DataFrame/Operations/Aggregation.hs
index 43c794ac..219fe9c9 100644
--- a/src/DataFrame/Operations/Aggregation.hs
+++ b/src/DataFrame/Operations/Aggregation.hs
@@ -20,8 +20,6 @@ import qualified Data.Vector.Algorithms.Merge as VA
 import qualified Data.Vector.Generic as VG
 import qualified Data.Vector.Mutable as VM
 import qualified Data.Vector.Unboxed as VU
-import qualified Statistics.Quantile as SS
-import qualified Statistics.Sample as SS
 
 import Control.Exception (throw)
 import Control.Monad (foldM_)
diff --git a/src/DataFrame/Operations/Statistics.hs b/src/DataFrame/Operations/Statistics.hs
index 62e9c83f..1352f680 100644
--- a/src/DataFrame/Operations/Statistics.hs
+++ b/src/DataFrame/Operations/Statistics.hs
@@ -62,7 +62,7 @@ median :: T.Text -> DataFrame -> Maybe Double
 median = applyStatistic median'
 
 standardDeviation :: T.Text -> DataFrame -> Maybe Double
-standardDeviation = applyStatistic SS.fastStdDev
+standardDeviation = applyStatistic (sqrt . variance')
 
 skewness :: T.Text -> DataFrame -> Maybe Double
 skewness = applyStatistic SS.skewness