What are VGChartz' sources for weekly US numbers?

[kn]

archmagus-21 said:

gebx said:

Alvar said:

Bodhesatva said:

Alvar said:

Bodhesatva said:

Alvar said:

Avinash_Tyagi said:

Alvar said:

 

 

 

 

 

Yes, but obviously the npd numbers have an order of magnitude lower error margin (as far as I understand it they have numbers from 60% of the market or something like that). And as I also said previously, VG-Chartz accuracy may be enough to warrant some discussion around the numbers, but don't assume they are correct numbers, since they could very well be off by a significant amount.

I don't think anyone assumes that the numbers are 100% accurate, but Vgcharts tries to get these numbers as accurate as possible.

Also this is the best and most indepth website on sales figures for videogames. No other website even comes close, so really if someone can find a website that offers what they do, and more accurately then please do provide a weblink.

Well, I just question the value of providing weekly numbers when those numbers are difficult or impossible to get even for professional marketing firms like NPD. And even NPD's monthly numbers are called into question at times, and they have, what, 65% coverage? With additional polling to further establish purchase patterns? I would much rather see VGChartz provide officially released numbers from recognized sales agencies rather than speculating independently. A 10% margin of error is pretty huge when you're talking about hundreds of thousands of units, and I know for a fact that on some months VGChartz' average margin of error is even higher.

 

You say you'd much rather VGC provide "official" numbers from "recognized" sales agences rather than speculating independently.   So you would rather VGC be "dependent" on other organization's data?  What, exactly, is the value in that?

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.