Re: probaility qns dse2013

Posted by Ashima on Mar 31, 2014; 4:48pm
URL: http://discussion-forum.276.s1.nabble.com/probaility-qns-dse2013-tp7585695p7585833.html

Guys, I guess it's 1/3

See when the letters come in post office, they do not have anything to do with first female or not.

There is an equal probability of getting m or f

p(m)= 1/2
p(f)= 1/2


Now , total number of cases are [ mm, ff, mf, fm]

prob of mm, ff, fm and fm (each)= 1/2x1/2= 1/4

But for post office mf and fm are same, so we can consider hem as one event(X), and thus there prob will be 1/4+1/4= 1/2

Now, ( prob of 2nd is female| the first is from female) = prob (intersection)/ prob of first is from female

                                                                       = ff/(ff+(ff+X)
                                                                       = 1/4/ (1/4+1/2)
                                                                       =1/4/3/4= 1/3