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Random vs Shuffle

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1372918.  Wed Jan 27, 2021 5:51 am Reply with quote

In episode 15. Random, there's a question regarding random music playlists and how the algorithm needed to be changed due to people perceiving randomness incorrectly. Throughout the explanation it's also referred to as 'shuffle', and they mention how if it were randomly selecting a song from your playlist you are just as likely to get the same song 3 times in a row as any other.
However, I would argue that there's a difference between random and shuffle.
Using a deck of cards as the example, each card represents a song. If I were to shuffle the deck (playlist) and play each card (song) one at a time, it would never repeat ones that have already been played - as it's simply taking the deck (playlist) and jumbling up the order before playing them in the resulting shuffled order. You would not get repeats until you reshuffled/restarted.
However with random, you would essentially reveal the card (play the song) put it back in the deck (playlist), shuffle again, and then reveal the next card (play the next song). Meaning the fact that a card (song) has already been played does not factor into the equation and you could get repeats.

1372941.  Wed Jan 27, 2021 9:13 am Reply with quote

It's still a random* process whether or not we allow the possibility of Song 2 being the same song as Song 1.

The difference is between selection with replacement (which you call random) and selection without replacement (which you call shuffle).

If we're going to listen to our music player for half an hour, we'd usually prefer not to get the same song twice - and so selection without replacement is probably best. That's a decision for the people who program the music player, but the process is still random whether or not we have replacement.

* OK, so strictly speaking it isn't, it's pseudorandom. But let's not got go there right now.

1373012.  Thu Jan 28, 2021 10:39 am Reply with quote

Don't get me wrong, I completely understand that shuffle is still random.

My point is that for music players the feature is listed as 'shuffle' and therefore selection without replacement, as detailed in my deck of cards comparison, because it doesn't reshuffle after each song is selected or played. It just mixes the order of the playlist and plays the songs one after the other.

My argument with regards to the explanation in the show is that the algorithm for a 'shuffle' feature is wrong if it allowed for repeats.
The whole point of this question was that they needed to change the algorithm so that this wouldn't happen because people felt it was favouring or ignoring songs.
If it was doing that, the feature should have been just called 'random' than specifically 'shuffle'. Therefore the wrong algorithm was used in the first place.


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