Using joint density to calculate probability that one person dies before the other












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Let $T_x, T_y$ be two random variables that describe the remaining lifetime of two persons aged $x$ and $y$, respectively. The joint density of $T_x$ and $T_y$ is given by



$$f_{T_x,T_y}(s,t)=begin{cases}frac{2}{45}cdot20^{-4}cdotBig(9 cdot 20^2-(3s-t)^2Big)&,s in [0,20], tin[0,60]\0&, mathrm{otherwise}end{cases}$$



How can I use this to determine the probability that the person aged $y$ dies before the person aged $x$?










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    $begingroup$


    Let $T_x, T_y$ be two random variables that describe the remaining lifetime of two persons aged $x$ and $y$, respectively. The joint density of $T_x$ and $T_y$ is given by



    $$f_{T_x,T_y}(s,t)=begin{cases}frac{2}{45}cdot20^{-4}cdotBig(9 cdot 20^2-(3s-t)^2Big)&,s in [0,20], tin[0,60]\0&, mathrm{otherwise}end{cases}$$



    How can I use this to determine the probability that the person aged $y$ dies before the person aged $x$?










    share|cite|improve this question









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      0








      0





      $begingroup$


      Let $T_x, T_y$ be two random variables that describe the remaining lifetime of two persons aged $x$ and $y$, respectively. The joint density of $T_x$ and $T_y$ is given by



      $$f_{T_x,T_y}(s,t)=begin{cases}frac{2}{45}cdot20^{-4}cdotBig(9 cdot 20^2-(3s-t)^2Big)&,s in [0,20], tin[0,60]\0&, mathrm{otherwise}end{cases}$$



      How can I use this to determine the probability that the person aged $y$ dies before the person aged $x$?










      share|cite|improve this question









      $endgroup$




      Let $T_x, T_y$ be two random variables that describe the remaining lifetime of two persons aged $x$ and $y$, respectively. The joint density of $T_x$ and $T_y$ is given by



      $$f_{T_x,T_y}(s,t)=begin{cases}frac{2}{45}cdot20^{-4}cdotBig(9 cdot 20^2-(3s-t)^2Big)&,s in [0,20], tin[0,60]\0&, mathrm{otherwise}end{cases}$$



      How can I use this to determine the probability that the person aged $y$ dies before the person aged $x$?







      probability






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      asked Jan 26 at 16:26









      user636610user636610

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          $begingroup$

          You need to integrate the joint density over the region where $T_y$ is less than $T_x$. I suggest drawing a picture. Your integration region is the rectangle $(s,t) in [0,20]times[0,60]$ where $s$ corresponds to $T_x$ and $t$ corresponds to $T_y$. If you draw the line $s = t$ you should be able to work out the limits of integration from there.






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          • $begingroup$
            So what are my limits of integration?
            $endgroup$
            – user636610
            Jan 26 at 17:30










          • $begingroup$
            I added some additional hints above. Short answer: draw a picture and it should be clear.
            $endgroup$
            – inhuretnakht
            Jan 26 at 18:24



















          0












          $begingroup$

          Draw a rectangle boundary for the joint PDF, where x axis in $[0,20]$ and y axis is $[0,60]$. We need $P(T_y<T_x)$. $y$ is smaller than $x$ below $y=x$ line. So, you need to integrate the joint in the region bounded by the lines $y=x, y=0, x=20$ as follows:



          $$P(T_y<T_x)=int_{0}^{20}int_{0}^{x}f(x,y)dydx$$






          share|cite|improve this answer









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            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            0












            $begingroup$

            You need to integrate the joint density over the region where $T_y$ is less than $T_x$. I suggest drawing a picture. Your integration region is the rectangle $(s,t) in [0,20]times[0,60]$ where $s$ corresponds to $T_x$ and $t$ corresponds to $T_y$. If you draw the line $s = t$ you should be able to work out the limits of integration from there.






            share|cite|improve this answer











            $endgroup$













            • $begingroup$
              So what are my limits of integration?
              $endgroup$
              – user636610
              Jan 26 at 17:30










            • $begingroup$
              I added some additional hints above. Short answer: draw a picture and it should be clear.
              $endgroup$
              – inhuretnakht
              Jan 26 at 18:24
















            0












            $begingroup$

            You need to integrate the joint density over the region where $T_y$ is less than $T_x$. I suggest drawing a picture. Your integration region is the rectangle $(s,t) in [0,20]times[0,60]$ where $s$ corresponds to $T_x$ and $t$ corresponds to $T_y$. If you draw the line $s = t$ you should be able to work out the limits of integration from there.






            share|cite|improve this answer











            $endgroup$













            • $begingroup$
              So what are my limits of integration?
              $endgroup$
              – user636610
              Jan 26 at 17:30










            • $begingroup$
              I added some additional hints above. Short answer: draw a picture and it should be clear.
              $endgroup$
              – inhuretnakht
              Jan 26 at 18:24














            0












            0








            0





            $begingroup$

            You need to integrate the joint density over the region where $T_y$ is less than $T_x$. I suggest drawing a picture. Your integration region is the rectangle $(s,t) in [0,20]times[0,60]$ where $s$ corresponds to $T_x$ and $t$ corresponds to $T_y$. If you draw the line $s = t$ you should be able to work out the limits of integration from there.






            share|cite|improve this answer











            $endgroup$



            You need to integrate the joint density over the region where $T_y$ is less than $T_x$. I suggest drawing a picture. Your integration region is the rectangle $(s,t) in [0,20]times[0,60]$ where $s$ corresponds to $T_x$ and $t$ corresponds to $T_y$. If you draw the line $s = t$ you should be able to work out the limits of integration from there.







            share|cite|improve this answer














            share|cite|improve this answer



            share|cite|improve this answer








            edited Jan 26 at 18:24

























            answered Jan 26 at 16:59









            inhuretnakhtinhuretnakht

            38617




            38617












            • $begingroup$
              So what are my limits of integration?
              $endgroup$
              – user636610
              Jan 26 at 17:30










            • $begingroup$
              I added some additional hints above. Short answer: draw a picture and it should be clear.
              $endgroup$
              – inhuretnakht
              Jan 26 at 18:24


















            • $begingroup$
              So what are my limits of integration?
              $endgroup$
              – user636610
              Jan 26 at 17:30










            • $begingroup$
              I added some additional hints above. Short answer: draw a picture and it should be clear.
              $endgroup$
              – inhuretnakht
              Jan 26 at 18:24
















            $begingroup$
            So what are my limits of integration?
            $endgroup$
            – user636610
            Jan 26 at 17:30




            $begingroup$
            So what are my limits of integration?
            $endgroup$
            – user636610
            Jan 26 at 17:30












            $begingroup$
            I added some additional hints above. Short answer: draw a picture and it should be clear.
            $endgroup$
            – inhuretnakht
            Jan 26 at 18:24




            $begingroup$
            I added some additional hints above. Short answer: draw a picture and it should be clear.
            $endgroup$
            – inhuretnakht
            Jan 26 at 18:24











            0












            $begingroup$

            Draw a rectangle boundary for the joint PDF, where x axis in $[0,20]$ and y axis is $[0,60]$. We need $P(T_y<T_x)$. $y$ is smaller than $x$ below $y=x$ line. So, you need to integrate the joint in the region bounded by the lines $y=x, y=0, x=20$ as follows:



            $$P(T_y<T_x)=int_{0}^{20}int_{0}^{x}f(x,y)dydx$$






            share|cite|improve this answer









            $endgroup$


















              0












              $begingroup$

              Draw a rectangle boundary for the joint PDF, where x axis in $[0,20]$ and y axis is $[0,60]$. We need $P(T_y<T_x)$. $y$ is smaller than $x$ below $y=x$ line. So, you need to integrate the joint in the region bounded by the lines $y=x, y=0, x=20$ as follows:



              $$P(T_y<T_x)=int_{0}^{20}int_{0}^{x}f(x,y)dydx$$






              share|cite|improve this answer









              $endgroup$
















                0












                0








                0





                $begingroup$

                Draw a rectangle boundary for the joint PDF, where x axis in $[0,20]$ and y axis is $[0,60]$. We need $P(T_y<T_x)$. $y$ is smaller than $x$ below $y=x$ line. So, you need to integrate the joint in the region bounded by the lines $y=x, y=0, x=20$ as follows:



                $$P(T_y<T_x)=int_{0}^{20}int_{0}^{x}f(x,y)dydx$$






                share|cite|improve this answer









                $endgroup$



                Draw a rectangle boundary for the joint PDF, where x axis in $[0,20]$ and y axis is $[0,60]$. We need $P(T_y<T_x)$. $y$ is smaller than $x$ below $y=x$ line. So, you need to integrate the joint in the region bounded by the lines $y=x, y=0, x=20$ as follows:



                $$P(T_y<T_x)=int_{0}^{20}int_{0}^{x}f(x,y)dydx$$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 26 at 18:52









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