Does this function define a probability function?












2












$begingroup$


Show that for a given random event $A$, the function $R: alpha rightarrow mathbb{R}$ defined as $R (B) = P (A | B)$ does not satisfy the axioms: https://en.wikipedia.org/wiki/Probability_axioms



$ alpha $ is the sigma-algebra



This is what I tried:



It is a simple counterexample: I have $A_{i}´s$ that belongs to $ alpha $. If I take the $emptyset$ set. So $R (B) = P (A | B)$ it is not well defined.



I am not sure. Any help? Am I right?



Also, If I define $P(B)>0$ of course my counterexmple doesnt work. How I could proof this?










share|cite|improve this question











$endgroup$

















    2












    $begingroup$


    Show that for a given random event $A$, the function $R: alpha rightarrow mathbb{R}$ defined as $R (B) = P (A | B)$ does not satisfy the axioms: https://en.wikipedia.org/wiki/Probability_axioms



    $ alpha $ is the sigma-algebra



    This is what I tried:



    It is a simple counterexample: I have $A_{i}´s$ that belongs to $ alpha $. If I take the $emptyset$ set. So $R (B) = P (A | B)$ it is not well defined.



    I am not sure. Any help? Am I right?



    Also, If I define $P(B)>0$ of course my counterexmple doesnt work. How I could proof this?










    share|cite|improve this question











    $endgroup$















      2












      2








      2





      $begingroup$


      Show that for a given random event $A$, the function $R: alpha rightarrow mathbb{R}$ defined as $R (B) = P (A | B)$ does not satisfy the axioms: https://en.wikipedia.org/wiki/Probability_axioms



      $ alpha $ is the sigma-algebra



      This is what I tried:



      It is a simple counterexample: I have $A_{i}´s$ that belongs to $ alpha $. If I take the $emptyset$ set. So $R (B) = P (A | B)$ it is not well defined.



      I am not sure. Any help? Am I right?



      Also, If I define $P(B)>0$ of course my counterexmple doesnt work. How I could proof this?










      share|cite|improve this question











      $endgroup$




      Show that for a given random event $A$, the function $R: alpha rightarrow mathbb{R}$ defined as $R (B) = P (A | B)$ does not satisfy the axioms: https://en.wikipedia.org/wiki/Probability_axioms



      $ alpha $ is the sigma-algebra



      This is what I tried:



      It is a simple counterexample: I have $A_{i}´s$ that belongs to $ alpha $. If I take the $emptyset$ set. So $R (B) = P (A | B)$ it is not well defined.



      I am not sure. Any help? Am I right?



      Also, If I define $P(B)>0$ of course my counterexmple doesnt work. How I could proof this?







      probability probability-theory measure-theory probability-distributions






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited Jan 11 at 23:43









      Bernard

      121k740116




      121k740116










      asked Jan 11 at 23:43









      LauraLaura

      2408




      2408






















          0






          active

          oldest

          votes











          Your Answer





          StackExchange.ifUsing("editor", function () {
          return StackExchange.using("mathjaxEditing", function () {
          StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
          StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
          });
          });
          }, "mathjax-editing");

          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "69"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: true,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: 10,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          noCode: true, onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3070452%2fdoes-this-function-define-a-probability-function%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          0






          active

          oldest

          votes








          0






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes
















          draft saved

          draft discarded




















































          Thanks for contributing an answer to Mathematics Stack Exchange!


          • Please be sure to answer the question. Provide details and share your research!

          But avoid



          • Asking for help, clarification, or responding to other answers.

          • Making statements based on opinion; back them up with references or personal experience.


          Use MathJax to format equations. MathJax reference.


          To learn more, see our tips on writing great answers.




          draft saved


          draft discarded














          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3070452%2fdoes-this-function-define-a-probability-function%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown





















































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown

































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown







          Popular posts from this blog

          MongoDB - Not Authorized To Execute Command

          in spring boot 2.1 many test slices are not allowed anymore due to multiple @BootstrapWith

          Npm cannot find a required file even through it is in the searched directory