Films in Common Percentage

[TheSaberfool]

I'm was playing around with this number a little bit and regenerating some PSI's. I'm not sure yet if there is one setting that is better than another as far as accurate predictions are concerned. So, I figured I'd ask the folks who have been around and used the site for a lot longer than I have what their findings are? What do you have your minimum set to? Do you find that the predictions are better for you at 10%? 50%? Have you found a "sweet spot" somewhere in the middle?

I took a quick look around and didn't see a discussion on the questions that I have in mind - so, if I missed it, go ahead and link me if you would.

[TheDenizen]

In my experience it's not necessarily the % but the # of films. I find to generate a reliable TCI with another user, you need to have at least 200-250 films in common. The % you use depends on the # of films you've rated. I've rated over 2700 movies, so I use 10%. But someone like yourself with around 1000 ratings would probably have better TCI/PSI results with a higher percentage, somewhere in the range of 20-25%...

[PeaceAnarchy]

200-250 or 10%, whichever is higher, sounds about right as a rule of thumb. If you're willing to play around with it, you can try different values and see where you're 1000th TCI ends up. The difference between 5% and 10% might not increase it by much, which means you're gaining more movie PSIs with little loss in accuracy, at the higher end you'll start losing more users so that it's no longer worthwhile. The sweet spot will really depend on what you watch. If most of your ratings are popular movies you can get away with a higher percentage than someone who only watches obscure movies.

[TheSaberfool]

Thanks for the input! The PSI was already doing a pretty damn good job once I hit >500 rankings, I just figured if there was a way too make them even better, someone would have already figured that out long before me.