Why do we define random variable models of probability distributions in the following manner. [closed]

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I am wondering why are random variable models of probability distributions defined like this:



Let X be the random variable that represents the NEXT measurement?







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closed as unclear what you're asking by Did, Xander Henderson, amWhy, Lord Shark the Unknown, max_zorn Aug 2 at 5:58


Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.


















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    I am wondering why are random variable models of probability distributions defined like this:



    Let X be the random variable that represents the NEXT measurement?







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    closed as unclear what you're asking by Did, Xander Henderson, amWhy, Lord Shark the Unknown, max_zorn Aug 2 at 5:58


    Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
















      up vote
      -2
      down vote

      favorite









      up vote
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      down vote

      favorite











      I am wondering why are random variable models of probability distributions defined like this:



      Let X be the random variable that represents the NEXT measurement?







      share|cite|improve this question











      I am wondering why are random variable models of probability distributions defined like this:



      Let X be the random variable that represents the NEXT measurement?









      share|cite|improve this question










      share|cite|improve this question




      share|cite|improve this question









      asked Aug 1 at 20:55









      Hello

      1




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      closed as unclear what you're asking by Did, Xander Henderson, amWhy, Lord Shark the Unknown, max_zorn Aug 2 at 5:58


      Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.






      closed as unclear what you're asking by Did, Xander Henderson, amWhy, Lord Shark the Unknown, max_zorn Aug 2 at 5:58


      Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.






















          2 Answers
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          It's just a formulation of your special case. Maybe it means exactly what's written there. Can't be answered without context tho.






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          • Thanks for your response.
            – Hello
            Aug 1 at 22:06

















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          Some authors use the word 'next' in connection with random variables to highlight the point that probability statements ought to be made only on experiments that have not been carried out yet, in which case there is some uncertainty about the result of the experiment; they don't apply to the observed result of an already-completed experiment, where all the uncertainty is gone.



          Example: Roll a die once. You can ask what is the probability that the next roll equals four. The answer is $P(X=4)=frac16$, where $X$ denotes the next roll. But if you carry out the experiment and observe a three, you can't substitute the observed value $3$ in place of $X$; there's no point in asking what is $P(3=4)$, and the answer is not $frac16$.



          It's not essential to use the word 'next' when talking about random variables, or probability in general, as long as it's understood that we are asking questions in the context of an experiment where uncertainty or chance plays a role. In that sense, the word 'next' is a way to insert a probability distribution into an experimental procedure; it's often shorthand for verbiage like 'pick a subject uniformly at random from a larger population'.






          share|cite|improve this answer




























            2 Answers
            2






            active

            oldest

            votes








            2 Answers
            2






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            0
            down vote













            It's just a formulation of your special case. Maybe it means exactly what's written there. Can't be answered without context tho.






            share|cite|improve this answer





















            • Thanks for your response.
              – Hello
              Aug 1 at 22:06














            up vote
            0
            down vote













            It's just a formulation of your special case. Maybe it means exactly what's written there. Can't be answered without context tho.






            share|cite|improve this answer





















            • Thanks for your response.
              – Hello
              Aug 1 at 22:06












            up vote
            0
            down vote










            up vote
            0
            down vote









            It's just a formulation of your special case. Maybe it means exactly what's written there. Can't be answered without context tho.






            share|cite|improve this answer













            It's just a formulation of your special case. Maybe it means exactly what's written there. Can't be answered without context tho.







            share|cite|improve this answer













            share|cite|improve this answer



            share|cite|improve this answer











            answered Aug 1 at 21:23









            til

            694




            694











            • Thanks for your response.
              – Hello
              Aug 1 at 22:06
















            • Thanks for your response.
              – Hello
              Aug 1 at 22:06















            Thanks for your response.
            – Hello
            Aug 1 at 22:06




            Thanks for your response.
            – Hello
            Aug 1 at 22:06










            up vote
            0
            down vote













            Some authors use the word 'next' in connection with random variables to highlight the point that probability statements ought to be made only on experiments that have not been carried out yet, in which case there is some uncertainty about the result of the experiment; they don't apply to the observed result of an already-completed experiment, where all the uncertainty is gone.



            Example: Roll a die once. You can ask what is the probability that the next roll equals four. The answer is $P(X=4)=frac16$, where $X$ denotes the next roll. But if you carry out the experiment and observe a three, you can't substitute the observed value $3$ in place of $X$; there's no point in asking what is $P(3=4)$, and the answer is not $frac16$.



            It's not essential to use the word 'next' when talking about random variables, or probability in general, as long as it's understood that we are asking questions in the context of an experiment where uncertainty or chance plays a role. In that sense, the word 'next' is a way to insert a probability distribution into an experimental procedure; it's often shorthand for verbiage like 'pick a subject uniformly at random from a larger population'.






            share|cite|improve this answer

























              up vote
              0
              down vote













              Some authors use the word 'next' in connection with random variables to highlight the point that probability statements ought to be made only on experiments that have not been carried out yet, in which case there is some uncertainty about the result of the experiment; they don't apply to the observed result of an already-completed experiment, where all the uncertainty is gone.



              Example: Roll a die once. You can ask what is the probability that the next roll equals four. The answer is $P(X=4)=frac16$, where $X$ denotes the next roll. But if you carry out the experiment and observe a three, you can't substitute the observed value $3$ in place of $X$; there's no point in asking what is $P(3=4)$, and the answer is not $frac16$.



              It's not essential to use the word 'next' when talking about random variables, or probability in general, as long as it's understood that we are asking questions in the context of an experiment where uncertainty or chance plays a role. In that sense, the word 'next' is a way to insert a probability distribution into an experimental procedure; it's often shorthand for verbiage like 'pick a subject uniformly at random from a larger population'.






              share|cite|improve this answer























                up vote
                0
                down vote










                up vote
                0
                down vote









                Some authors use the word 'next' in connection with random variables to highlight the point that probability statements ought to be made only on experiments that have not been carried out yet, in which case there is some uncertainty about the result of the experiment; they don't apply to the observed result of an already-completed experiment, where all the uncertainty is gone.



                Example: Roll a die once. You can ask what is the probability that the next roll equals four. The answer is $P(X=4)=frac16$, where $X$ denotes the next roll. But if you carry out the experiment and observe a three, you can't substitute the observed value $3$ in place of $X$; there's no point in asking what is $P(3=4)$, and the answer is not $frac16$.



                It's not essential to use the word 'next' when talking about random variables, or probability in general, as long as it's understood that we are asking questions in the context of an experiment where uncertainty or chance plays a role. In that sense, the word 'next' is a way to insert a probability distribution into an experimental procedure; it's often shorthand for verbiage like 'pick a subject uniformly at random from a larger population'.






                share|cite|improve this answer













                Some authors use the word 'next' in connection with random variables to highlight the point that probability statements ought to be made only on experiments that have not been carried out yet, in which case there is some uncertainty about the result of the experiment; they don't apply to the observed result of an already-completed experiment, where all the uncertainty is gone.



                Example: Roll a die once. You can ask what is the probability that the next roll equals four. The answer is $P(X=4)=frac16$, where $X$ denotes the next roll. But if you carry out the experiment and observe a three, you can't substitute the observed value $3$ in place of $X$; there's no point in asking what is $P(3=4)$, and the answer is not $frac16$.



                It's not essential to use the word 'next' when talking about random variables, or probability in general, as long as it's understood that we are asking questions in the context of an experiment where uncertainty or chance plays a role. In that sense, the word 'next' is a way to insert a probability distribution into an experimental procedure; it's often shorthand for verbiage like 'pick a subject uniformly at random from a larger population'.







                share|cite|improve this answer













                share|cite|improve this answer



                share|cite|improve this answer











                answered Aug 1 at 22:23









                grand_chat

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                17.8k11120












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