Is Random.org Skewed?

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On my reviews and giveaways blog, I’ve noticed a lot of people enter my contests on the last day. I’m not exactly sure why, but I have two theories about this. First, some readers enter at the last minute to minimize the impact of their tweets. When they tweet about my giveaway at 11pm Pacific time on the last day of the giveaway, fewer people will see it compared to other times.

My other theory is that my readers read somewhere that random.org favors higher numbers. I don’t think random.org favors higher numbers, but to be certain I decided to do a little test. I used random.org to select a number from one to ten. I did this manually one hundred times while watching Inception (I can’t be sure but someone may have planted this blog post idea in my head). Take a look at the results:

random.org numbers distribution - 100 times
Generated 100 times

As you can see in the above chart, random.org favored 1’s, 5’s, 6’s, 8’s, and 9’s. I was hoping the numbers would be evenly distributed (generated ten times each), but this is not the case. This actually makes sense because each number is generated randomly and has a 10% chance of being generated each time. Regardless of which numbers have already been generated, the probability does not increase or decrease. It’s always 10% each time (for ten numbers) and because it’s random, you will see random results like the graphics above. For instance, when I ran the random numbers generator another 50 times, I got something completely different. This time around, random.org favored 3’s, 7’s, and 9’s.

random.org numbers distribution - 50 times
Generated 50 times

[Update: A reader emailed me and said a more likely explanation is that my giveaways are posted onto sweepstaking websites and forums and people usually sort by end date to make sure they don’t miss something — thus they’re not even aware of my contest until the day it ends. Makes sense to me.]

10 thoughts on “Is Random.org Skewed?

  1. That is really interesting! I read the same thing about random favoring early and late numbers, but didn’t think it could be true since I lose so much. :)

    I enter on the last day because that way I know I’ve only entered once. I just had my third baby and have a hard time remembering if I ate lunch, much less which contests I’ve entered. I was worried I’d enter something twice and be disqualified, so I started entering the last day only. I usually don’t get a break until the kids are in bed for the night, so it ends up being almost at the last minute since most contests end at midnight.

    If there’s a way to check and see if I’ve entered already (and there probably is), I would love to know about it. I’ve been reading a lot of these blogs for a long time, but just started entering a couple of months ago, so I’m probably doing things wrong.

  2. It does seem like a lot of my winners enter early or late, but I think that’s because I get most of the entries on the first and last day of the giveaway.

  3. I like to enter contests just as soon as I find them. If its a contest where each tweet or what ever is another entry, then the more I get the better my odds. Also when some one is doing a giveaway and promoting a product, I feel I should do my part to help promote by tweeting or what ever to help spread the word, to say thanks for doing the giveaway. I have no choice but to trust that the contest is run on the up and up. Unfortunately all are not. I once won a Dell netbook, never got it, and all of a sudden the Twitter account that ran the contest disappeared. But for the most part, since I have gotten to win so many things from so many great bloggers and companies, that things seem pretty fair to me!!

    1. I’m actually having problems with itsthoughtful.com. I promoted their contest last November, but they have not sent the $25 Amazon gift card to my giveaway winner. I’ve been emailing them the last three weeks, but they still have not replied. Not very thoughtful, are they?

  4. I always enter giveaways on the last day or two. This is mainly because I keep a big list of all the giveaways I want to enter, and I enter them in order of end date. I never have enough time to enter more than a day or two’s worth at one time. I usually don’t tweet if it is the last couple minutes of the giveaway (yes, I often am down to the wire… I work evenings, so am usually rushed at the end of the night!) because I don’t feel it is right to get credit for doing so… I really never even considered that fewer people would hear about the giveaway! I also had never heard that random.org favored bigger numbers! I never even would have noticed that!

    1. Another reader said the same thing about entering giveaways based on end date. Sounds like a good idea for people who enter multiple giveaways. Otherwise, you’ll have to keep track of which giveaways you’ve entered.

  5. i have to agree, i sort mine by the end date and then enter. i have entered yours and won before! (thanks!)

    i love the research you did on random!

  6. I’ve always wondered about that. I used to enter a lot of giveaways but gave up because I only won a few times. A friend of mine said she won several books a week from various book blogs and I could never figure out how she could do that – I wonder if she knew this ??

    1. I only enter a few giveaways a year and rarely win. I’m hopeful when I enter, but I assume I won’t win because the ones I enter tend to have thousands of entries.

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