Probability problem of Birth Rate and GDP












1












$begingroup$


Ronnie obtained data about the gross domestic product (GDP) and the birth rate for 170 countries.
He classified each GDP and each birth rate as either ‘low’, ‘medium’ or ‘high’. The table shows the
number of countries in each category.



enter image description here



One country is chosen at random from those countries which have a medium GDP and then a different
country is chosen at random from those which have a medium birth rate. Find the probability that both countries chosen have a medium GDP and a medium birth rate.



P.S. This is a question from Cambridge Advanced Subsidiary Level and Advanced Level



My Try



I tried this with a Tree Diagram. First set of branches as Medium GDP and Second Set of branches as Medium Birth Rate.This got me the answer $frac{42}{74}timesfrac{42}{55}$.



First I need to know if this is correct.Secondly
can you help me to do this using conditional probability? Thanks a lot.










share|cite|improve this question









$endgroup$

















    1












    $begingroup$


    Ronnie obtained data about the gross domestic product (GDP) and the birth rate for 170 countries.
    He classified each GDP and each birth rate as either ‘low’, ‘medium’ or ‘high’. The table shows the
    number of countries in each category.



    enter image description here



    One country is chosen at random from those countries which have a medium GDP and then a different
    country is chosen at random from those which have a medium birth rate. Find the probability that both countries chosen have a medium GDP and a medium birth rate.



    P.S. This is a question from Cambridge Advanced Subsidiary Level and Advanced Level



    My Try



    I tried this with a Tree Diagram. First set of branches as Medium GDP and Second Set of branches as Medium Birth Rate.This got me the answer $frac{42}{74}timesfrac{42}{55}$.



    First I need to know if this is correct.Secondly
    can you help me to do this using conditional probability? Thanks a lot.










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      Ronnie obtained data about the gross domestic product (GDP) and the birth rate for 170 countries.
      He classified each GDP and each birth rate as either ‘low’, ‘medium’ or ‘high’. The table shows the
      number of countries in each category.



      enter image description here



      One country is chosen at random from those countries which have a medium GDP and then a different
      country is chosen at random from those which have a medium birth rate. Find the probability that both countries chosen have a medium GDP and a medium birth rate.



      P.S. This is a question from Cambridge Advanced Subsidiary Level and Advanced Level



      My Try



      I tried this with a Tree Diagram. First set of branches as Medium GDP and Second Set of branches as Medium Birth Rate.This got me the answer $frac{42}{74}timesfrac{42}{55}$.



      First I need to know if this is correct.Secondly
      can you help me to do this using conditional probability? Thanks a lot.










      share|cite|improve this question









      $endgroup$




      Ronnie obtained data about the gross domestic product (GDP) and the birth rate for 170 countries.
      He classified each GDP and each birth rate as either ‘low’, ‘medium’ or ‘high’. The table shows the
      number of countries in each category.



      enter image description here



      One country is chosen at random from those countries which have a medium GDP and then a different
      country is chosen at random from those which have a medium birth rate. Find the probability that both countries chosen have a medium GDP and a medium birth rate.



      P.S. This is a question from Cambridge Advanced Subsidiary Level and Advanced Level



      My Try



      I tried this with a Tree Diagram. First set of branches as Medium GDP and Second Set of branches as Medium Birth Rate.This got me the answer $frac{42}{74}timesfrac{42}{55}$.



      First I need to know if this is correct.Secondly
      can you help me to do this using conditional probability? Thanks a lot.







      probability






      share|cite|improve this question













      share|cite|improve this question











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      share|cite|improve this question










      asked Jan 15 at 9:19









      emilemil

      438410




      438410






















          1 Answer
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          $begingroup$

          Your answer is almost correct.



          Overlooked in the calculation is that we are dealing with two different countries.



          Let $B_1$ correspond with birth rate of firstly chosen country.



          Let $G_2$ correspond with GDP of secondly chosen country.



          Taking into account on forehand (so that no conditions for that are needed anymore) that the GDP of the first chosen country is "median" and the birth rate of the second chosen country is "median" we find:$$P(B_1=text{median}wedge G_2=text{median})=P(B_1=text{median})P(G_2=text{median}mid B_1=text{median})=frac{42}{74}frac{41}{54}$$



          Under condition "$B_1=text{median}$" there are $55-1=54$ countries left that can be picked as second choice, and $42-1=41$ of them give "median" for GDP.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Help is Highly Appreciated!
            $endgroup$
            – emil
            Jan 15 at 11:22










          • $begingroup$
            I am glad to help.
            $endgroup$
            – drhab
            Jan 15 at 11:23












          Your Answer





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          1 Answer
          1






          active

          oldest

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          active

          oldest

          votes






          active

          oldest

          votes









          1












          $begingroup$

          Your answer is almost correct.



          Overlooked in the calculation is that we are dealing with two different countries.



          Let $B_1$ correspond with birth rate of firstly chosen country.



          Let $G_2$ correspond with GDP of secondly chosen country.



          Taking into account on forehand (so that no conditions for that are needed anymore) that the GDP of the first chosen country is "median" and the birth rate of the second chosen country is "median" we find:$$P(B_1=text{median}wedge G_2=text{median})=P(B_1=text{median})P(G_2=text{median}mid B_1=text{median})=frac{42}{74}frac{41}{54}$$



          Under condition "$B_1=text{median}$" there are $55-1=54$ countries left that can be picked as second choice, and $42-1=41$ of them give "median" for GDP.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Help is Highly Appreciated!
            $endgroup$
            – emil
            Jan 15 at 11:22










          • $begingroup$
            I am glad to help.
            $endgroup$
            – drhab
            Jan 15 at 11:23
















          1












          $begingroup$

          Your answer is almost correct.



          Overlooked in the calculation is that we are dealing with two different countries.



          Let $B_1$ correspond with birth rate of firstly chosen country.



          Let $G_2$ correspond with GDP of secondly chosen country.



          Taking into account on forehand (so that no conditions for that are needed anymore) that the GDP of the first chosen country is "median" and the birth rate of the second chosen country is "median" we find:$$P(B_1=text{median}wedge G_2=text{median})=P(B_1=text{median})P(G_2=text{median}mid B_1=text{median})=frac{42}{74}frac{41}{54}$$



          Under condition "$B_1=text{median}$" there are $55-1=54$ countries left that can be picked as second choice, and $42-1=41$ of them give "median" for GDP.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            Help is Highly Appreciated!
            $endgroup$
            – emil
            Jan 15 at 11:22










          • $begingroup$
            I am glad to help.
            $endgroup$
            – drhab
            Jan 15 at 11:23














          1












          1








          1





          $begingroup$

          Your answer is almost correct.



          Overlooked in the calculation is that we are dealing with two different countries.



          Let $B_1$ correspond with birth rate of firstly chosen country.



          Let $G_2$ correspond with GDP of secondly chosen country.



          Taking into account on forehand (so that no conditions for that are needed anymore) that the GDP of the first chosen country is "median" and the birth rate of the second chosen country is "median" we find:$$P(B_1=text{median}wedge G_2=text{median})=P(B_1=text{median})P(G_2=text{median}mid B_1=text{median})=frac{42}{74}frac{41}{54}$$



          Under condition "$B_1=text{median}$" there are $55-1=54$ countries left that can be picked as second choice, and $42-1=41$ of them give "median" for GDP.






          share|cite|improve this answer









          $endgroup$



          Your answer is almost correct.



          Overlooked in the calculation is that we are dealing with two different countries.



          Let $B_1$ correspond with birth rate of firstly chosen country.



          Let $G_2$ correspond with GDP of secondly chosen country.



          Taking into account on forehand (so that no conditions for that are needed anymore) that the GDP of the first chosen country is "median" and the birth rate of the second chosen country is "median" we find:$$P(B_1=text{median}wedge G_2=text{median})=P(B_1=text{median})P(G_2=text{median}mid B_1=text{median})=frac{42}{74}frac{41}{54}$$



          Under condition "$B_1=text{median}$" there are $55-1=54$ countries left that can be picked as second choice, and $42-1=41$ of them give "median" for GDP.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jan 15 at 10:14









          drhabdrhab

          104k545136




          104k545136












          • $begingroup$
            Help is Highly Appreciated!
            $endgroup$
            – emil
            Jan 15 at 11:22










          • $begingroup$
            I am glad to help.
            $endgroup$
            – drhab
            Jan 15 at 11:23


















          • $begingroup$
            Help is Highly Appreciated!
            $endgroup$
            – emil
            Jan 15 at 11:22










          • $begingroup$
            I am glad to help.
            $endgroup$
            – drhab
            Jan 15 at 11:23
















          $begingroup$
          Help is Highly Appreciated!
          $endgroup$
          – emil
          Jan 15 at 11:22




          $begingroup$
          Help is Highly Appreciated!
          $endgroup$
          – emil
          Jan 15 at 11:22












          $begingroup$
          I am glad to help.
          $endgroup$
          – drhab
          Jan 15 at 11:23




          $begingroup$
          I am glad to help.
          $endgroup$
          – drhab
          Jan 15 at 11:23


















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