diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5164567..164385b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,10 @@
 ## 1.0.26
 
-- Fix `IterableNumExtension.standardDeviation`.
+- Fix:
+  - `IterableNumExtension.standardDeviation`.
+  - `IterableDoubleExtension.standardDeviation`.
+  - `DecimalOnIterableDecimalExtension.standardDeviation`.
+  - `DynamicIntOnIterableDynamicNumberExtension.standardDeviation`.
 
 - sdk: '>=2.14.0 <4.0.0'
 - intl: ^0.18.1
diff --git a/lib/src/statistics_decimal.dart b/lib/src/statistics_decimal.dart
index 02cf7ce..0b0d4df 100644
--- a/lib/src/statistics_decimal.dart
+++ b/lib/src/statistics_decimal.dart
@@ -1666,7 +1666,7 @@ extension DecimalOnIterableDecimalExtension on Iterable<Decimal> {
 
     var average = mean;
 
-    var first = itr.current;
+    var first = itr.current - average;
     var total = first * first;
 
     while (itr.moveNext()) {
diff --git a/lib/src/statistics_dynamic_int.dart b/lib/src/statistics_dynamic_int.dart
index e0c5b54..876efa6 100644
--- a/lib/src/statistics_dynamic_int.dart
+++ b/lib/src/statistics_dynamic_int.dart
@@ -1610,7 +1610,7 @@ extension DynamicIntOnIterableDynamicNumberExtension
 
     var average = mean;
 
-    var first = itr.current;
+    var first = itr.current - average;
     var total = first * first;
 
     while (itr.moveNext()) {
@@ -1690,7 +1690,7 @@ extension DynamicIntOnIterableDynamicIntExtension on Iterable<DynamicInt> {
 
     var average = mean;
 
-    var first = itr.current;
+    var first = itr.current - average;
     var total = first * first;
 
     while (itr.moveNext()) {
diff --git a/lib/src/statistics_extension_num.dart b/lib/src/statistics_extension_num.dart
index a1d85c1..8817d6a 100644
--- a/lib/src/statistics_extension_num.dart
+++ b/lib/src/statistics_extension_num.dart
@@ -439,7 +439,7 @@ extension IterableDoubleExtension on Iterable<double> {
 
     var average = mean;
 
-    var first = itr.current;
+    var first = itr.current - average;
     var total = first * first;
 
     while (itr.moveNext()) {
@@ -731,7 +731,7 @@ extension IterableIntExtension on Iterable<int> {
 
     var average = mean;
 
-    var first = itr.current;
+    var first = itr.current - average;
     var total = (first * first).toDouble();
 
     while (itr.moveNext()) {
diff --git a/test/statistics_extension_num_test.dart b/test/statistics_extension_num_test.dart
index 5e80d76..f5c03ab 100644
--- a/test/statistics_extension_num_test.dart
+++ b/test/statistics_extension_num_test.dart
@@ -266,8 +266,8 @@ void main() {
     test('standardDeviation', () {
       expect(<int>[].standardDeviation, equals(0));
       expect([0].standardDeviation, equals(0));
-      expect([10].standardDeviation, equals(10));
-      expect([10, 20].standardDeviation, equals(7.905694150420948));
+      expect([10].standardDeviation, equals(0));
+      expect([10, 20].standardDeviation, equals(5));
       expect(<int>[10, 20, 30].standardDeviation, equals(8.16496580927726));
     });
 
@@ -551,8 +551,8 @@ void main() {
     test('standardDeviation', () {
       expect(<double>[].standardDeviation, equals(0));
       expect(<double>[0.0].standardDeviation, equals(0));
-      expect(<double>[10.0].standardDeviation, equals(10));
-      expect(<double>[10.0, 20.0].standardDeviation, equals(7.905694150420948));
+      expect(<double>[10.0].standardDeviation, equals(0));
+      expect(<double>[10.0, 20.0].standardDeviation, equals(5));
       expect(<double>[10.0, 20.0, 30.0].standardDeviation,
           equals(8.16496580927726));
     });