# What are the odds?

**URL:** <https://boards.straightdope.com/t/what-are-the-odds/663579>\
**Category:** Miscellaneous and Personal Stuff I Must Share\
**Created:** [July 15, 2013, 6:38pm UTC](https://boards.straightdope.com/t/what-are-the-odds/663579 "2013-07-15T18:38:13Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\
**Post date:** [July 15, 2013, 6:38pm UTC](https://boards.straightdope.com/t/what-are-the-odds/663579/1 "2013-07-15T18:38:13Z")

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Something just happened that I am curious about. I have 2997 songs on Winamp. It turns out that I have some repeats of songs. Most songs are represented only once. A small number are listed twice, and I think only one song is repeated 3 times.

When I load the player I shuffle the order of the songs and reverse the order as well. This is done randomly to ensure a nice mix in the play list. Is there any way to calculate the odds of same song showing up three times in a row?

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**Author:** ![DataX](https://avatars.discourse-cdn.com/v4/letter/d/e99b99/32.png) [@DataX](https://boards.straightdope.com/u/DataX)\
**Post date:** [July 15, 2013, 7:04pm UTC](https://boards.straightdope.com/t/what-are-the-odds/663579/2 "2013-07-15T19:04:54Z")

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What is the purpose of reversing the songs after the shuffle?

Lets assume for the sake of argument - to see what the odds are on the low end - every song is repeated three times. To make the math easy - assume 3000 songs.

So 1,000 unique songs.

After every song plays - there is a 1 out of 1000 chance it will play again (not sure if shuffle is different from random - as in doesn’t allow repeats - but assume repeats are allowed).

This means you have a 1 in 1000 chance of hearing a song twice in a row.

Every thousand times or so this will happen - what are the chances of it happening a third time? Multiply that by 1,000 - so 1 in a million.

So using conservative rules - or liberal I guess - you have no greater than a 1 in 1,000,000 chance of hearing the same song three times in a row.

This assumes the random number generator is truly random of course.

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**Author:** ![Manduck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/manduck/32/256_2.png) [@Manduck](https://boards.straightdope.com/u/Manduck)\
**Post date:** [July 15, 2013, 7:11pm UTC](https://boards.straightdope.com/t/what-are-the-odds/663579/3 "2013-07-15T19:11:09Z")

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If the songs are shuffled, the only songs that could possibly come up three times in a row are the ones that you have three copies of. If we knew how many of those there are, somebody could easily do the math. Not me, but somebody 🙂

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**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\
**Post date:** [July 15, 2013, 7:18pm UTC](https://boards.straightdope.com/t/what-are-the-odds/663579/4 "2013-07-15T19:18:45Z")

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These are assuming that that winamp uses a perfect random number generator. I have to assume that it’s better then when I used it 10 years ago, but back then it was awful. Hearing the same songs over and over was pretty normal. I had about 1500+ songs, I shuffled the list and then told it to pick randomly. It was like it picked a group of about 10 near the top and a group of about 10 near the bottom and just kept flipping back and forth between those two groups all night.