diff --git a/src/Math-Core-Distribution/PMNormalDistribution.class.st b/src/Math-Core-Distribution/PMNormalDistribution.class.st
index e0a948d7a..bced833aa 100644
--- a/src/Math-Core-Distribution/PMNormalDistribution.class.st
+++ b/src/Math-Core-Distribution/PMNormalDistribution.class.st
@@ -8,9 +8,22 @@ Class {
 	#classVars : [
 		'NextRandom'
 	],
-	#category : 'Math-Core-Distribution'
+	#category : #'Math-Core-Distribution'
 }
 
+{ #category : #information }
+PMNormalDistribution class >> boxMullerTransform [
+|v1 v2 w y|
+			[ v1 := Number random * 2 - 1.
+			v2 := Number random * 2 - 1.
+			w := v1 squared + v2 squared.
+			w > 1 ] whileTrue.
+			y := (w ln * 2 negated / w) sqrt.
+			v1 := y * v1.
+			NextRandom := y * v2.
+			^v1.
+]
+
 { #category : #information }
 PMNormalDistribution class >> distributionName [
 	
@@ -41,20 +54,15 @@ PMNormalDistribution class >> new: aNumber1 sigma: aNumber2 [
 { #category : #information }
 PMNormalDistribution class >> random [
 	"Answer a random number distributed according to a (0,1) normal distribution."
-	| v1 v2 w y |
-	NextRandom isNil
-		ifTrue: [ [ v1 := Number random * 2 - 1.
-					v2 := Number random * 2 - 1.
-					w := v1 squared + v2 squared.
-					w > 1 ] whileTrue: [].
-				  y := ( ( w ln * 2 negated) / w) sqrt.
-				v1 := y * v1.
-				NextRandom := y * v2.
-				]
-		ifFalse:[ v1 :=NextRandom.
-				  NextRandom := nil.
-				].
-	^v1
+
+	| v1  |
+	NextRandom
+		ifNil: [
+			
+			v1 := self boxMullerTransform ]
+		ifNotNil: [ v1 := NextRandom.
+			NextRandom := nil ].
+	^ v1
 ]
 
 { #category : #information }
@@ -78,10 +86,8 @@ PMNormalDistribution >> distributionValue: aNumber [
 
 { #category : #initialization }
 PMNormalDistribution >> initialize: aNumber1 sigma: aNumber2 [
-
 	mu := aNumber1.
-	sigma := aNumber2.
-	^self
+	sigma := aNumber2
 ]
 
 { #category : #information }
@@ -98,8 +104,9 @@ PMNormalDistribution >> parameters [
 
 { #category : #information }
 PMNormalDistribution >> random [
-	"Answer a random number distributed accroding to the receiver."
-	^self class random * sigma + mu
+	"Answer a random number distributed according to the receiver."
+
+	^ self class random * sigma + mu
 ]
 
 { #category : #information }
diff --git a/src/Math-Numerical/Number.extension.st b/src/Math-Numerical/Number.extension.st
index 31ef61b6a..a16408381 100644
--- a/src/Math-Numerical/Number.extension.st
+++ b/src/Math-Numerical/Number.extension.st
@@ -70,15 +70,16 @@ Number >> productWithVector: aVector [
 ]
 
 { #category : #'*Math-Numerical' }
-Number >> random [
-		"Answers a random number distributed between 0 and the receiver."
-	^self class random * self
+Number class >> random [
+	"Answers a floating random number between 0 and 1 excluded"
+
+	^ PMMitchellMooreGenerator new floatValue
 ]
 
 { #category : #'*Math-Numerical' }
-Number class >> random [
-		"Answers a random number between 0 and the receiver."
-	^ PMMitchellMooreGenerator new floatValue
+Number >> random [
+		"Answers a random number distributed between 0 and the receiver."
+	^self class random * self
 ]
 
 { #category : #'*Math-Numerical' }
diff --git a/src/Math-Numerical/PMCauchyDistribution.class.st b/src/Math-Numerical/PMCauchyDistribution.class.st
index 50e2bffbc..6b8d05e11 100644
--- a/src/Math-Numerical/PMCauchyDistribution.class.st
+++ b/src/Math-Numerical/PMCauchyDistribution.class.st
@@ -59,10 +59,10 @@ PMCauchyDistribution >> distributionValue: aNumber [
 
 { #category : #initialization }
 PMCauchyDistribution >> initialize: aNumber1 scale: aNumber2 [
-	"Private - Initialize the parameters of the receiver. "
+	"Initialize the parameters of the receiver. "
+
 	mu := aNumber1.
-	beta := aNumber2.
-	^self
+	beta := aNumber2
 ]
 
 { #category : #information }
diff --git a/src/Math-Numerical/PMExponentialDistribution.class.st b/src/Math-Numerical/PMExponentialDistribution.class.st
index 495f5e3ac..962727adb 100644
--- a/src/Math-Numerical/PMExponentialDistribution.class.st
+++ b/src/Math-Numerical/PMExponentialDistribution.class.st
@@ -66,8 +66,7 @@ PMExponentialDistribution >> initialize: aNumber [
 
 	aNumber > 0
 		ifFalse: [ self error: 'Illegal distribution parameters' ].
-	beta := aNumber.
-	^ self
+	beta := aNumber
 ]
 
 { #category : #information }
diff --git a/src/Math-Numerical/PMFisherTippettDistribution.class.st b/src/Math-Numerical/PMFisherTippettDistribution.class.st
index fa9e30269..39a78a546 100644
--- a/src/Math-Numerical/PMFisherTippettDistribution.class.st
+++ b/src/Math-Numerical/PMFisherTippettDistribution.class.st
@@ -68,12 +68,12 @@ PMFisherTippettDistribution >> distributionValue: aNumber [
 
 { #category : #initialization }
 PMFisherTippettDistribution >> initialize: aNumber1 scale: aNumber2 [
-		"Private - Initialize the parameters of the receiver."
-	aNumber2 > 0
-		ifFalse: [ self error: 'Illegal distribution parameters'].
+	"Initialize the parameters of the receiver."
+
+	aNumber2 <= 0
+		ifTrue: [ self error: 'Illegal distribution parameters' ].
 	alpha := aNumber1.
-	beta := aNumber2.
-	^self
+	beta := aNumber2
 ]
 
 { #category : #information }
@@ -104,11 +104,12 @@ PMFisherTippettDistribution >> parameters [
 
 { #category : #information }
 PMFisherTippettDistribution >> random [
-		"Answer a random number distributed according to the receiver."
+	"Answer a random number distributed according to the receiver."
+
 	| t |
 	[ t := flatGenerator floatValue ln negated.
-	  t > 0] whileFalse: [].
-	^t ln negated * beta + alpha
+	t > 0 ] whileFalse.
+	^ t ln negated * beta + alpha
 ]
 
 { #category : #information }