Confusion over term “uniformly distributed” in a probability problem












0














I'm trying to determine a joint PDF for random variables $X$ and $Y$ in this problem:



$(X,Y)$ is uniformly distributed on the subset of $mathbb R^2$, defined by $0<X<2$ and $0 <Y<X^3$.



I'm not sure I understand what's meant by "uniformly distributed". Are they saying all valid $(X,Y)$ combinations have equal probability? How does one even begin to define a joint PDF for this?



Would it be something like



$f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$
Where $k$ is some positive constant










share|cite|improve this question



























    0














    I'm trying to determine a joint PDF for random variables $X$ and $Y$ in this problem:



    $(X,Y)$ is uniformly distributed on the subset of $mathbb R^2$, defined by $0<X<2$ and $0 <Y<X^3$.



    I'm not sure I understand what's meant by "uniformly distributed". Are they saying all valid $(X,Y)$ combinations have equal probability? How does one even begin to define a joint PDF for this?



    Would it be something like



    $f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$
    Where $k$ is some positive constant










    share|cite|improve this question

























      0












      0








      0







      I'm trying to determine a joint PDF for random variables $X$ and $Y$ in this problem:



      $(X,Y)$ is uniformly distributed on the subset of $mathbb R^2$, defined by $0<X<2$ and $0 <Y<X^3$.



      I'm not sure I understand what's meant by "uniformly distributed". Are they saying all valid $(X,Y)$ combinations have equal probability? How does one even begin to define a joint PDF for this?



      Would it be something like



      $f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$
      Where $k$ is some positive constant










      share|cite|improve this question













      I'm trying to determine a joint PDF for random variables $X$ and $Y$ in this problem:



      $(X,Y)$ is uniformly distributed on the subset of $mathbb R^2$, defined by $0<X<2$ and $0 <Y<X^3$.



      I'm not sure I understand what's meant by "uniformly distributed". Are they saying all valid $(X,Y)$ combinations have equal probability? How does one even begin to define a joint PDF for this?



      Would it be something like



      $f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$
      Where $k$ is some positive constant







      probability probability-distributions






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Nov 22 '18 at 13:34









      HumptyDumptyHumptyDumpty

      33518




      33518






















          1 Answer
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          2














          It means



          $$f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$$



          where $k$ is a positive constant.



          To find $k$, we have to find the area of the support.



          we have $$k^{-1}= int_0^2 x^3 , dx$$






          share|cite|improve this answer























          • What do you mean by "area of the suppose"?
            – HumptyDumpty
            Nov 22 '18 at 13:40










          • oops, typo, i meant support
            – Siong Thye Goh
            Nov 22 '18 at 13:40










          • I've computed $k = 1/4$. How does one interpret this result?
            – HumptyDumpty
            Nov 22 '18 at 13:47










          • Your $k$ value is correct. hmm... if you pick two area of the size over the support and call them event $A$ and $B$, we know that the probability of $A$ is equal to the probability of $B$. It just depends on the area.
            – Siong Thye Goh
            Nov 22 '18 at 13:51











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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          2














          It means



          $$f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$$



          where $k$ is a positive constant.



          To find $k$, we have to find the area of the support.



          we have $$k^{-1}= int_0^2 x^3 , dx$$






          share|cite|improve this answer























          • What do you mean by "area of the suppose"?
            – HumptyDumpty
            Nov 22 '18 at 13:40










          • oops, typo, i meant support
            – Siong Thye Goh
            Nov 22 '18 at 13:40










          • I've computed $k = 1/4$. How does one interpret this result?
            – HumptyDumpty
            Nov 22 '18 at 13:47










          • Your $k$ value is correct. hmm... if you pick two area of the size over the support and call them event $A$ and $B$, we know that the probability of $A$ is equal to the probability of $B$. It just depends on the area.
            – Siong Thye Goh
            Nov 22 '18 at 13:51
















          2














          It means



          $$f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$$



          where $k$ is a positive constant.



          To find $k$, we have to find the area of the support.



          we have $$k^{-1}= int_0^2 x^3 , dx$$






          share|cite|improve this answer























          • What do you mean by "area of the suppose"?
            – HumptyDumpty
            Nov 22 '18 at 13:40










          • oops, typo, i meant support
            – Siong Thye Goh
            Nov 22 '18 at 13:40










          • I've computed $k = 1/4$. How does one interpret this result?
            – HumptyDumpty
            Nov 22 '18 at 13:47










          • Your $k$ value is correct. hmm... if you pick two area of the size over the support and call them event $A$ and $B$, we know that the probability of $A$ is equal to the probability of $B$. It just depends on the area.
            – Siong Thye Goh
            Nov 22 '18 at 13:51














          2












          2








          2






          It means



          $$f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$$



          where $k$ is a positive constant.



          To find $k$, we have to find the area of the support.



          we have $$k^{-1}= int_0^2 x^3 , dx$$






          share|cite|improve this answer














          It means



          $$f_{X,Y}(x,y) = begin{cases}k,&0<X<2, 0 <Y<X^3 \0,& text{otherwise} end{cases}$$



          where $k$ is a positive constant.



          To find $k$, we have to find the area of the support.



          we have $$k^{-1}= int_0^2 x^3 , dx$$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Nov 22 '18 at 13:40

























          answered Nov 22 '18 at 13:37









          Siong Thye GohSiong Thye Goh

          100k1465117




          100k1465117












          • What do you mean by "area of the suppose"?
            – HumptyDumpty
            Nov 22 '18 at 13:40










          • oops, typo, i meant support
            – Siong Thye Goh
            Nov 22 '18 at 13:40










          • I've computed $k = 1/4$. How does one interpret this result?
            – HumptyDumpty
            Nov 22 '18 at 13:47










          • Your $k$ value is correct. hmm... if you pick two area of the size over the support and call them event $A$ and $B$, we know that the probability of $A$ is equal to the probability of $B$. It just depends on the area.
            – Siong Thye Goh
            Nov 22 '18 at 13:51


















          • What do you mean by "area of the suppose"?
            – HumptyDumpty
            Nov 22 '18 at 13:40










          • oops, typo, i meant support
            – Siong Thye Goh
            Nov 22 '18 at 13:40










          • I've computed $k = 1/4$. How does one interpret this result?
            – HumptyDumpty
            Nov 22 '18 at 13:47










          • Your $k$ value is correct. hmm... if you pick two area of the size over the support and call them event $A$ and $B$, we know that the probability of $A$ is equal to the probability of $B$. It just depends on the area.
            – Siong Thye Goh
            Nov 22 '18 at 13:51
















          What do you mean by "area of the suppose"?
          – HumptyDumpty
          Nov 22 '18 at 13:40




          What do you mean by "area of the suppose"?
          – HumptyDumpty
          Nov 22 '18 at 13:40












          oops, typo, i meant support
          – Siong Thye Goh
          Nov 22 '18 at 13:40




          oops, typo, i meant support
          – Siong Thye Goh
          Nov 22 '18 at 13:40












          I've computed $k = 1/4$. How does one interpret this result?
          – HumptyDumpty
          Nov 22 '18 at 13:47




          I've computed $k = 1/4$. How does one interpret this result?
          – HumptyDumpty
          Nov 22 '18 at 13:47












          Your $k$ value is correct. hmm... if you pick two area of the size over the support and call them event $A$ and $B$, we know that the probability of $A$ is equal to the probability of $B$. It just depends on the area.
          – Siong Thye Goh
          Nov 22 '18 at 13:51




          Your $k$ value is correct. hmm... if you pick two area of the size over the support and call them event $A$ and $B$, we know that the probability of $A$ is equal to the probability of $B$. It just depends on the area.
          – Siong Thye Goh
          Nov 22 '18 at 13:51


















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