kn said:
Do you realize the irony of that statement? NPD numbers are "official" in only one way: They are the official NPD numbers. Beyond that, they are a statistical estimation of sales. Period. They are "recognized" in that they report their "official" numbers and are pretty much the only game in town. NPDs numbers are "independent" in that they gather data, statisically analyze it, and report it but are completely dependent on the data they gather from retail and distribution channels. VGC's sampling data, estimating, statisically projecting, etc. is no different than NPD and it doesn't make their numbers any less independent or dependent as well as any more or less official. VGC most certainly is estimating sales (just like NPD is an estimate) on a smaller budget and a smaller data set but that doesn't make VGC's numbers any less "offical"... You said you have a higher degree in statistics. While my degree isn't in statistics, I have taken quite a number in my studies in support of my chosen field. There is no doubt that a larger sample will reduce deviation, but it is entirely possible to create fairly high quality estimates with small sample sizes. If the entire population was acting independently, sample size would have to be huge. Since, in every entry in the sales charts for both hardware and software, each and every entry is a "single" sku, the need for sampling is to account for overall variances between different stores and regions. Given past history of how each area in the U.S. along with how close each store tracks compared to others, it would be quite possible to get a pretty darn high i.e. 90% confidence with a very small sample size. Only ioi knows his statistical methods and I'm sure he won't be sharing them with us. (I certainly wouldn't) Give it six more months and see how things are going in terms of his predictions. As with anything statistical, over time we'll know more accurately how well his sales statistics compare to other data. So far I'm fairly impressed with his results given the resources and time involved to produce such data. |
To clarify:
1. I see (or used to see) VGChartz as a "one stop shop" for collected sales data. Meaning, I didn't have to go to half a dozen different sites to try to find sales. Regardless of whether I wanted NPD monthly US sales, weekly Japanese sales, worldwide shipment numbers, etc., I could just come to VGChartz. But since VGChartz started reporting weekly US numbers, I'm not sure at all about what is "official" and what is "independent" on this site. That's why I posted this thread in the first place: if I'm going to keep coming here to find out sales data, I want to know how reliable VGChartz' numbers are compared to the official numbers.
2. I never said I had a higher degree in statistics. That was another poster. I have taken a basic statistics course in college, but that was a while ago.
