Monday, January 31, 2011

Blu Ray Media: Raw Quality Data

Blu Ray blank media guide : Best Blu Ray media brands
Best Blu Ray Media Brands Part 3: Raw Quality Data

What are the best Blu Ray media/disc brands for data storage and archival? To answer this question, we collected reviews from over 1,100 users across the web (1,120 reviews to be precise:-), using over 20 primary and 60 secondary sources. We collated all the results by brand and model. For each model, we kept track of the number of positive and negative reviews, and tagged negative reviews for the following reasons: compatibility, coasters, and the dreaded archival failure. We also kept track of pricing, and identified, for each product, a low-cost vendor (we will review all pricing information in our sections on Blu Ray online stores). The raw quality data can be reviewed below.

Table 1: Raw quality data for Blu Ray media
It is immediately apparent that, while some products have large numbers of reviews which are statistically sufficient to establish archival quality (or the lack thereof), many have few or no reviews. We were, however, able to establish, in the large majority of cases, a very good estimate of predictive quality, based on the following factors:
  • overall Blu Ray brand quality
  • overall quality of the Blu Ray media manufacturer
  • overall quality for the brand in the DVD market.
We created a custom predictive quality rating for Blu Ray media. To create a quality rating for each brand, starting with the raw data available above, we used the following process:
  • we allocated 75% of the feedback to the brand, and 25% to the manufacturer when we knew who it was. In many cases, the manufacturer was the company identified by the MID - but that was not always the case.  For the manufacturer quality rating, we averaged the raw review rating across all brands sharing the same manufacturer.  
  • we multiplied the % of negative reviews due to archival failure (the worst type, since it results in data loss) by 5, to penalize heavily brands with a record of archival failure.
  • when we had track record for the brand in the DVD market, we added 10 fictitious reviews with the brand DVD quality rating to the Blu Ray reviews. We did not use the DVD quality rating for those brands that are factoring in the DVD arena but OEMing in the Blu Ray market (or vice versa), since the circumstances between the two markets would be too different.
  • when we had too few reviews to guarantee, through statistical analysis, at most 5% error with 95% certainty, we corrected the rating downward until the margin of error downwards was only 5%. For instance, if the quality rating of a brand was 92%, but the margin of error was 12% given the sample size, we lowered the quality rating down to 85%, so that the maximum margin of error downwards was only 5%: in this case, the interval of 95% certainty would be [80%, 100%], and we picked 85% as the predictive quality rating. This means that our predictive quality ratings give a worst case picture of quality expectations when sample size is small. 
  • the result was the brand's Blu Ray media predictive quality rating. A perfect rating would be 100% and would mean that all reviews were positive, that the company's DVD media quality rating was perfect (if it had one), and that the sample size for the Blu Ray media user reviews was large enough to have a statistical error margin of 5% or less with 95% certainty. If this sounds difficult - it is, yet several brands score higher than 90%, and two score over 95%!
In the following sections, we review brand quality brand by brand... So come back soon!

To understand Blu Ray lingo, check our lexicon of Blu Ray vocabulary. Our Blu Ray brand predictive quality rating process is explained here. Our statistical analysis practices are described here, which is also where we discuss's predictive quality rating.

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Unknown said...

Excellent summary; just what I was looking for! Skipped the whole DVD craze and am jumping from a CD-ROM burner to a Blu-Ray burner finally. It's a minefield out there when it comes to media. Thanks for the posts and keep them coming!

George Gear said...

Thanks Kirk! We are now publishing a series on the best Blu Ray online stores - hope you will like it too!

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