اذا كان ا . ب حدثين متنافيين من فضاء عينة ف لتجربة عشوائية وكان :
ل ( ا ) = ل (ا ) , ل (ب ) = \frac{1}{2} ل ( ا ) فأوجد :
(i ) ل (ب )
( ii ) ل ( ا - ب )
( iii ) ل ( أ $\cap$∩ ب )
$(1)\becauseل(ا)$(1)∵ل(ا)= ل (ا )
$\therefore$∴ ل (ا ) = $\frac{1}{2}$12 ل ( ا ) = $\frac{1}{4}$14
( ii ) ل ( ا - ب ) = ل ( ا ) - ل ( ا $\cap$∩ ب )
= $\frac{1}{2}$12 - صفر = $\frac{1}{2}$12
( iii ) ل ( ا $\cap$∩ ب ) = 1 - ل ( ا $\cup$∪ )
= 1 - [ ل (ا ) + ل (ب ) ]
= 1- [ $\frac{1}{2}$12 + $\frac{1}{4}$14 ]
= $\frac{1}{4}$14