Question 478970
your table is as follows if i understand it correctly:
<pre>
             employed         unemployed
male           67761               2433
female         58655               2285
</pre>
the question is:
find the probability of selecting a person who is employed, given that the person is male.
if you are given that the person is male, then the probability of getting an employed male is the number of employed males divided by the total number of males.
that would be:
{{{67761 / (67761 + 2433) = .965338918}}}
the probability of getting an employed male is .965338918.
this is because .965338918 * the total number of males is employed.
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there is a formula that says that:
p(e|m) = {{{p(e and m) / p(m)}}}
this formula states:
the probability of e given m is equal to the probability of (e intersect m) divided by the probability of m.
e is employed
m is male.
this formula will also give you the same answer, but the numbers are derived as follows:
<pre>
            employed          unemployed         total
male          67761              2433            70164
female        58655              2285            60940
total        126416              4718           131134
</pre>
p(e and m) is equal to {{{67761 / 131134 = .516730977}}}
p(m) is equal to {{{70164 / 131134 = .535055745}}}
p(e|m) =  {{{p(e and m) / p(m) = .516730977 / .535055745 = .965338918}}}
it's exactly the same as we derived above.
in the first way we figured it out, our universe became only the men.
in the second way we figured it out, our universe was everybody.
the formulas give you the same number.
the first method was {{{67761 / 70164}}} which was the number of employed males divided by the total number of males.
the second method was:
{{{p(e and m) / p(m)}}}
{{{p(e and m) = 67761 / 131134}}}
{{{p(m) = 70164 / 131134}}}
{{{p(e and m) / p(m)}}} becomes {{{(67761/131134) / (70164/131134)}}} which is equivalent to:
{{{(67761/131134) * (131134/70164)}}} which is equivalent to:
{{{(67761 * 131134) / (131134 * 70164)}}}
the 131134 in the numerator and the denominator cancel out and your are left with:
{{{(67761/70164)}}}.
either way gets you the same answer.