Question 1122116
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I came to fix the solution to Problem A given by the tutor @rothauserc, which is wrong.



We have to interpret the condition in this way:


<pre>
    15% of children in a community school system come from low-income families 
    and the rest  100%-15% = 85%  come from not low-income families.
</pre>

Now, the problem asks what is the probability that the applicant having a college degree comes from a low income family.


It is the "conditional" probability.


So the solution is


<pre>
    the probability under the question is  {{{(0.15*0.2)/(0.15*0.2 + 0.85*0.4)}}} =  0.081081 = 8.1%  (approximately).
</pre>

The denominator is the probability that the applicant has a college degree.


Solved.