More iTunes Math

markmcb writes "OmniNerd once again digs into the math behind iTunes. The 5-star ratings in iTunes are actually stored in a variable allowing values from 0 to 100, with 20 = 1-star, 40 = 2-star, etc. Known to few, if you set a rating to 30 (manually), it will show up as 1 1/2 stars in the program's GUI. Matt Schinckel provides interesting statistical evidence showing that not only do non-whole, non-half values (e.g., 47) not increase the amount a song will play, but neither do the half-star ratings (with the exception of .5 star)."

Comments

How does the Windows version work?

[CyricZ]

Has anyone been able to replicate this behavior with the Windows version of iTunes? Is it built upon the same core as the Mac OS version, or does Apple have a separate implementation that may behave differently?

Re:How does it handle values outside the range?

[frostilicus2]

I've just tried this - If you insert a value outside the range, iTunes assumes the nearest value to 0, 20, 40, 60, 80, and 100 and doesn't crash.

closed source..

[GrAfFiT]

Interesting to see that what would just involve reading a few lines of code on open source software takes a whole complicated statistical analysis on closed source software...

why linear?

[kavehkh]

Why is the rating system linear instead of exponential. I would like a song that has one more star than another to play TWICE more often.

Re:why linear?

[NeMon'ess]

I agree that the fixed settings suck. As a user actually comfortable operating a computer, unlike much of the market, I want advanced options that let me adjust how much more and less often I hear songs. So Party Shuffle isn't worth using to me.

Instead I rate my tracks like I would a movie.
1-star is probably going to get deleted eventually.
2-stars play half as much as No-stars.
No-stars play twice as much as 2-stars.
3-stars play 3 times as much as 2-stars.
4-stars play 4 times as much as 2-stars.
5-stars play 6 times as much as 2-stars.

Then I make an enormous playlist containing 1 play of 2-star songs, 2 plays of No-star songs... and 6 plays of 5-star songs, shuffle them, and save the result in a new playlist. Takes between 3 and 5 months to go through the list.

5 Stars Rating Systems are Poor Design

[ChristopherA]

If you read my article on the Rating Systems you'll see that 5 point rating systems are a poor way to do ratings. In our analysis, only 10% of raters use the bottom two star in a 5-point scale, and only 2% use the lowest rating of 1 star. The median of the 5-point scale is actually the fourth star, with a neat bell curve arranged around it. In my own personal use of iTunes, I've forced myself to be much more consistent and lower with my ratings. 1 star means that it has been rated, but in general I don't like it and don't play it. 2 stars means average, which means play it some of the time. 3 stars is above average, and play it more often, but I can get bored with these. 4 is good, and can basically listen to these regularly without getting tired. 5 stars are exemplars -- I try to find more songs like these.

Re:5 Stars Rating Systems are Poor Design

[ibennetch]

I think this is because people tend to think of a 5-point rating system as being 5 stars for love it and 0 for hate it -- where as if they hate a song, they probably don't even own it. Even "strongly dislike" which is what most people would figure as 1 or 2 stars, doesn't make the cut to be purchased for my music collection. I like your system, where 5 is exceptionally good and 2 is average; it's much more useful for this type of thing because the music that would typically get rated 0, 1, or 2 isn't even in one's music collection, so the whole rating system needs to compensate for that.