diff --git a/dataframe-operations.cabal b/dataframe-operations.cabal
--- a/dataframe-operations.cabal
+++ b/dataframe-operations.cabal
@@ -1,6 +1,6 @@
 cabal-version:      3.4
 name:               dataframe-operations
-version:            2.5.0.0
+version:            2.5.0.1
 synopsis:           Column operations, expression DSL, and statistics for the dataframe ecosystem.
 description:
     Untyped column operations (select, filter, sort, join, groupBy,
diff --git a/src-internal/DataFrame/Internal/Statistics.hs b/src-internal/DataFrame/Internal/Statistics.hs
--- a/src-internal/DataFrame/Internal/Statistics.hs
+++ b/src-internal/DataFrame/Internal/Statistics.hs
@@ -106,7 +106,7 @@
 computeSkewness :: SkewAcc -> Double
 computeSkewness (SkewAcc n _ m2 m3)
     | n < 3 = 0 -- or error "skewness of <3 samples"
-    | otherwise = (sqrt (fromIntegral n - 1) * m3) / sqrt (m2 ^ (3 :: Int))
+    | otherwise = (sqrt (fromIntegral n) * m3) / sqrt (m2 ^ (3 :: Int))
 {-# INLINE computeSkewness #-}
 
 skewness' :: (VU.Unbox a, Real a, Num a) => VU.Vector a -> Double
@@ -202,11 +202,14 @@
 {-# INLINE interQuartileRange' #-}
 
 meanSquaredError :: VU.Vector Double -> VU.Vector Double -> Maybe Double
-meanSquaredError target prediction =
-    let
-        squareDiff = VU.ifoldl' (\sq i e -> (e - target VU.! i) ^ (2 :: Int) + sq) 0 prediction
-     in
-        Just $ squareDiff / fromIntegral (max (VU.length target) (VU.length prediction))
+meanSquaredError target prediction
+    | VU.length target /= VU.length prediction = Nothing
+    | VU.null target = Nothing
+    | otherwise =
+        Just
+            ( VU.sum (VU.zipWith (\t p -> (p - t) ^ (2 :: Int)) target prediction)
+                / fromIntegral (VU.length target)
+            )
 {-# INLINE meanSquaredError #-}
 
 mutualInformationBinned ::
diff --git a/src/DataFrame/Functions.hs b/src/DataFrame/Functions.hs
--- a/src/DataFrame/Functions.hs
+++ b/src/DataFrame/Functions.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE BangPatterns #-}
 {-# LANGUAGE DisambiguateRecordFields #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
@@ -317,10 +318,10 @@
     Agg
         ( MergeAgg
             "mean"
-            (MeanAcc 0.0 0)
-            (\(MeanAcc s c) x -> MeanAcc (s + realToFrac x) (c + 1))
-            (\(MeanAcc s1 c1) (MeanAcc s2 c2) -> MeanAcc (s1 + s2) (c1 + c2))
-            (\(MeanAcc s c) -> if c == 0 then 0 / 0 else s / fromIntegral c)
+            ((0.0, 0) :: (Double, Int))
+            (\(!s, !c) x -> (s + realToFrac x, c + 1))
+            (\(!s1, !c1) (!s2, !c2) -> (s1 + s2, c1 + c2))
+            (\(s, c) -> if c == 0 then 0 / 0 else s / fromIntegral c)
         )
 {-# SPECIALIZE mean :: Expr Double -> Expr Double #-}
 {-# SPECIALIZE mean :: Expr Float -> Expr Double #-}
diff --git a/src/DataFrame/Operations/Typing.hs b/src/DataFrame/Operations/Typing.hs
--- a/src/DataFrame/Operations/Typing.hs
+++ b/src/DataFrame/Operations/Typing.hs
@@ -355,7 +355,10 @@
         EitherRead -> fromVector (V.map ((readEitherRaw @a) . toStr) col)
 
     asType :: SafeReadMode -> SchemaType -> Column -> Column
-    asType mode st c@(PackedText _ _) = asType mode st (materializePacked c)
+    asType mode st@(SType (_ :: P.Proxy a)) c@(PackedText _ _) =
+        case testEquality (typeRep @a) (typeRep @T.Text) of
+            Just Refl -> c
+            Nothing -> asType mode st (materializePacked c)
     asType mode (SType (_ :: P.Proxy a)) c@(BoxedColumn _ (col :: V.Vector b)) = case typeRep @a of
         App t1 _t2 -> case eqTypeRep t1 (typeRep @Maybe) of
             Just HRefl -> case testEquality (typeRep @a) (typeRep @b) of