Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
Skins
  • Light
  • Brite
  • Cerulean
  • Cosmo
  • Flatly
  • Journal
  • Litera
  • Lumen
  • Lux
  • Materia
  • Minty
  • Morph
  • Pulse
  • Sandstone
  • Simplex
  • Sketchy
  • Spacelab
  • United
  • Yeti
  • Zephyr
  • Dark
  • Cyborg
  • Darkly
  • Quartz
  • Slate
  • Solar
  • Superhero
  • Vapor

  • Default (No Skin)
  • No Skin
Collapse

The New Coffee Room

  1. TNCR
  2. General Discussion
  3. Puzzle time: the runt of random points

Puzzle time: the runt of random points

Scheduled Pinned Locked Moved General Discussion
11 Posts 3 Posters 56 Views
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • jon-nycJ Online
    jon-nycJ Online
    jon-nyc
    wrote on last edited by
    #1

    Choose 10 numbers uniformly at random from the unit interval [0,1].

    On average, what is the value of their minimum?

    The whole reason we call them illegal aliens is because they’re subject to our laws.

    1 Reply Last reply
    • HoraceH Offline
      HoraceH Offline
      Horace
      wrote on last edited by Horace
      #2

      :::

      I suppose the number where there's a 50/50 shot of never randomly choosing below it in 10 tries.

      :::

      Education is extremely important.

      jon-nycJ 1 Reply Last reply
      • HoraceH Horace

        :::

        I suppose the number where there's a 50/50 shot of never randomly choosing below it in 10 tries.

        :::

        jon-nycJ Online
        jon-nycJ Online
        jon-nyc
        wrote on last edited by
        #3

        @horace And that number would be?

        The whole reason we call them illegal aliens is because they’re subject to our laws.

        1 Reply Last reply
        • jon-nycJ Online
          jon-nycJ Online
          jon-nyc
          wrote on last edited by
          #4

          Hint:

          :::

          Think circle, not line.

          :::

          The whole reason we call them illegal aliens is because they’re subject to our laws.

          HoraceH 1 Reply Last reply
          • HoraceH Offline
            HoraceH Offline
            Horace
            wrote on last edited by
            #5

            :::

            .5=(1-n)^10

            =0.066967

            :::

            Education is extremely important.

            1 Reply Last reply
            • jon-nycJ jon-nyc

              Hint:

              :::

              Think circle, not line.

              :::

              HoraceH Offline
              HoraceH Offline
              Horace
              wrote on last edited by
              #6

              @jon-nyc said in Puzzle time: the runt of random points:

              Hint:

              :::

              Think circle, not line.

              :::

              Right, my formula would give the median but not the mean. Higher minimums have more room for outliers than lower minimums, which can only go to zero.

              Education is extremely important.

              1 Reply Last reply
              • KlausK Offline
                KlausK Offline
                Klaus
                wrote on last edited by
                #7

                :::

                If you choose 1 number, the average of the mimimum is 0.5.
                With 2 numbers, it's 0.333. With 3 it's 0.25.

                With n numbers it's 1/(n+1), hence for 10 it's 0.909...
                :::

                1 Reply Last reply
                • jon-nycJ Online
                  jon-nycJ Online
                  jon-nyc
                  wrote on last edited by jon-nyc
                  #8

                  Klaus is right.

                  Well, that was my answer. Official solution comes Saturday.

                  :::

                  One way to think about it is as follows: Pick 11 random points on a unit circumference circle (expected distance between points is 1/11). Randomly pick one as marking start/end point of unit line.

                  :::

                  The whole reason we call them illegal aliens is because they’re subject to our laws.

                  1 Reply Last reply
                  • HoraceH Offline
                    HoraceH Offline
                    Horace
                    wrote on last edited by
                    #9

                    I'm sure that's right.

                    Education is extremely important.

                    1 Reply Last reply
                    • jon-nycJ Online
                      jon-nycJ Online
                      jon-nyc
                      wrote on last edited by
                      #10

                      @Horace My original intuition was similar to yours but with a different formula.

                      The probabilities would be additive, not multiplicative, no?

                      So if m is the expected minimum value, that meant that:

                      10 * p(x<m) = 0.5, or
                      p(x<m) = 0.05
                      which gave me 1/20.

                      But as you pointed out that would be a median value, the mean would be higher than that.

                      The whole reason we call them illegal aliens is because they’re subject to our laws.

                      HoraceH 1 Reply Last reply
                      • jon-nycJ jon-nyc

                        @Horace My original intuition was similar to yours but with a different formula.

                        The probabilities would be additive, not multiplicative, no?

                        So if m is the expected minimum value, that meant that:

                        10 * p(x<m) = 0.5, or
                        p(x<m) = 0.05
                        which gave me 1/20.

                        But as you pointed out that would be a median value, the mean would be higher than that.

                        HoraceH Offline
                        HoraceH Offline
                        Horace
                        wrote on last edited by Horace
                        #11

                        @jon-nyc said in Puzzle time: the runt of random points:

                        @Horace My original intuition was similar to yours but with a different formula.

                        The probabilities would be additive, not multiplicative, no?

                        So if m is the expected minimum value, that meant that:

                        10 * p(x<m) = 0.5, or
                        p(x<m) = 0.05
                        which gave me 1/20.

                        But as you pointed out that would be a median value, the mean would be higher than that.

                        My formula gives the correct median. It's the chance of rolling higher than "x" 10 times in a row, so multiplicative.

                        Education is extremely important.

                        1 Reply Last reply

                        Hello! It looks like you're interested in this conversation, but you don't have an account yet.

                        Getting fed up of having to scroll through the same posts each visit? When you register for an account, you'll always come back to exactly where you were before, and choose to be notified of new replies (either via email, or push notification). You'll also be able to save bookmarks and upvote posts to show your appreciation to other community members.

                        With your input, this post could be even better 💗

                        Register Login
                        Reply
                        • Reply as topic
                        Log in to reply
                        • Oldest to Newest
                        • Newest to Oldest
                        • Most Votes


                        • Login

                        • Don't have an account? Register

                        • Login or register to search.
                        • First post
                          Last post
                        0
                        • Categories
                        • Recent
                        • Tags
                        • Popular
                        • Users
                        • Groups