Predication algoritm works less good for favorite movies?

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MockHamill
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Predication algoritm works less good for favorite movies?

Post by MockHamill »

I have rated 1211 movies and tv-series so far, and I understand the TCI and PSI system.
The site is typically very accurate and tend to predict my ratings +-5 on most cases.
However, for movies/tv-series in the 90+ range the sites predictions tend to be off by a much larger number.

Is this a general flaw in the system, or it something that happens to only me?
And if this generally occurring, what is the reason?

CosmicMonkey
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Re: Predication algoritm works less good for favorite movies?

Post by CosmicMonkey »

Are you using the percentile system or are you still on the tier system?

One of the biggest things I noticed after switching to percentile system is that the PSIs on the extreme ends, both top and bottom, tended to uh... not be as extreme (I think regression to the mean is the technical term but idk, math was always my worst subject). Whereas before I would regularly have PSIs of 98, 99, or sometimes even 100, after switching to the percentile system I rarely have PSIs over 90. So yeah, it's less likely to accurately predict the films you'll absolutely love (or hate), but at the same time it's less likely to give you a PSI of 100 for a film that you only give a 90, and overall, I think it's still a more accurate that way than the way it was before.

MockHamill
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Joined: Wed Nov 12, 2008 9:52 pm

Re: Predication algoritm works less good for favorite movies?

Post by MockHamill »

I am using the percentile system.
Maybe the system need to have separate TCI for top and bottom movies only.
Many of my top movies are off by 15 points (like I grade a movie 100, the system guess 85).

So basically while the system is good at predicting if I find a movie good or not, it is bad at figuring out if I will find a movie/tv-serie amazing. Which is a serious flaw.

kgbelliveau
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Re: Predication algoritm works less good for favorite movies?

Post by kgbelliveau »

I generally find since switching from the tier system to the percentile system that most of my PSI's are from 60 to 85 which also happens to be the bulk of where my ratings are. Perhaps it is attempting to categorize the scores based on the type of film. A lot of my lower rankings are cheesy C movie horror and terrible romantic comedies and childrens films. Even what I will likely rate as a 85 or higher horror flick (Get Out, It and Dont Breathe) to name a few all had lower PSI because of my past ranking history with the horror films of the late 90s and early 00s.

I try not to pay much attention to PSI. It is a cool idea but in my case I have so many extreme variances where I was given a PSI of 74 and ended up scoring the film like a 90 or higher. Aquaman was the most recent example of this.

fra paolo
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Re: Predication algoritm works less good for favorite movies?

Post by fra paolo »

MockHamill wrote:So basically while the system is good at predicting if I find a movie good or not, it is bad at figuring out if I will find a movie/tv-serie amazing. Which is a serious flaw.

I don't know if it is a serious flaw. I am not a statistical mathematician, but I thought it was very difficult to design a predictive formula that can forecast extreme results.Those projection systems used by baseball fans cannot. So this 'flaw' is inherent in the method.

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