+ Reply to Thread
Results 1 to 7 of 7

Thread: 818 Facebook Friends, 0 Birthdays

  1. #1
    Points: 21, Level: 1
    Level completed: 41%, Points required for next Level: 29

    Posts
    2
    Thanks
    0
    Thanked 0 Times in 0 Posts

    818 Facebook Friends, 0 Birthdays




    Hi all, first time poster here. I am an avid facebooker and like to wish people happy birthdays when they come up. Today, for the first time, I noticed that 0 birthdays fell on this particular day.

    This got me thinking about what the statistical probability of this happening is...818 friends, 365 days in a year, and 0 birthdays. It's been a while for me since my last Stats class, so I was hoping someone could help me out!

    Thanks,

    Kevin

  2. #2
    TS Contributor
    Points: 12,501, Level: 73
    Level completed: 13%, Points required for next Level: 349

    Posts
    951
    Thanks
    0
    Thanked 103 Times in 100 Posts

    Re: 818 Facebook Friends, 0 Birthdays

    2 months ago similar question

    An answer is (1 - 1/365.25)^818

  3. #3
    Points: 21, Level: 1
    Level completed: 41%, Points required for next Level: 29

    Posts
    2
    Thanks
    0
    Thanked 0 Times in 0 Posts

    Re: 818 Facebook Friends, 0 Birthdays

    Hi Mean Joe, is this the same as (364/365)^818?
    Last edited by kmac1112; 08-21-2012 at 01:23 PM.

  4. #4
    Points: 24, Level: 1
    Level completed: 47%, Points required for next Level: 26

    Posts
    3
    Thanks
    1
    Thanked 0 Times in 0 Posts

    Re: 818 Facebook Friends, 0 Birthdays

    I've also noticed that when I increase the value of friends from 818 to a higher #, the % decreases with your formula. This doesn't seem right.

    I can't seem to figure this one out either.

  5. #5
    Omega Contributor
    Points: 38,432, Level: 100
    Level completed: 0%, Points required for next Level: 0
    hlsmith's Avatar
    Location
    Not Ames, IA
    Posts
    7,006
    Thanks
    398
    Thanked 1,186 Times in 1,147 Posts

    Re: 818 Facebook Friends, 0 Birthdays

    I don't think you are performing the calculations in the right order, it works for me.

    1/365.25 = 0.0027378508
    1 - 0.0027378508 = 0.9972621492
    0.9972621492^818 = 0.1061785301, seems correct.
    Substitute 900 for 818 and got 0.0847898311, seems correct.

  6. The Following User Says Thank You to hlsmith For This Useful Post:

    KLaw Squared (08-21-2012)

  7. #6
    Points: 24, Level: 1
    Level completed: 47%, Points required for next Level: 26

    Posts
    3
    Thanks
    1
    Thanked 0 Times in 0 Posts

    Re: 818 Facebook Friends, 0 Birthdays

    Okay, I think I've got it. The end result is the % odds that no one has a birthday on that date, meaning the higher the sample, the lower the %. Thanks.

  8. #7
    Omega Contributor
    Points: 38,432, Level: 100
    Level completed: 0%, Points required for next Level: 0
    hlsmith's Avatar
    Location
    Not Ames, IA
    Posts
    7,006
    Thanks
    398
    Thanked 1,186 Times in 1,147 Posts

    Re: 818 Facebook Friends, 0 Birthdays


    364/365 = 1-(1/365), so yes, but when you add the 0.25 slight discrepancies emerge between the numbers.

+ Reply to Thread

           




Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts






Advertise on Talk Stats