| MaskedBandit2 said: http://www.barb.co.uk/resources/reference-documents/how-we-do-what-we-do This is a better page to include - an actual, detailed explanation for how the data is gathered. And again, you didn't respond to me directly, so I'll say it again - You cannot take such a tiny portion of a market (if you're even getting any data for a particular title during that week, which I highly doubt you can receive for every game out there) and balloon it out to a precise and exact number to the nearest unit and rank them. I don't care what page is added, it's impossible and the final figures appear misleading because of it. It's a matter of integrity and professionalism. It's one thing if you're covering the majority of a particular market and you can say with reasonable confidence one game sold X amount over the other, but that's not the case here. |
I'm guessing you haven't studied statistics.
Sampling works exactly as ioi has described, and the resulting numbers are typically scaled up directly (plus adjustments for known biases), rather than rounding roughly. Why? Because every time you round, you lose further information. And then when you sum over a lot of numbers, the error gets worse. Sampling error is bad enough as it is, you don't want to make it worse with rounding.
Sampling error itself follows a fairly simple rule. To work out the margin of error for a 95% confidence interval, for a large population, you can approximate it using 0.98/sqrt(n), where n is the number of samples. So, for that BARB thing, a sample of 11,000 will provide a margin of error of 0.93%. But they'll still note that Strictly Come Dancing got 11.07 million, despite the 0.07 being within the margin of error. And they'll still list The One Show on Tuesday having higher ratings than The One Show on Monday despite the difference being 0.01 million, well below the margin of error.
The reason is that people like things ranked. It's not the purpose of the site to rank them, but to provide the numbers. The ranking is for regular users, and makes for a bit more enjoyment from debating the numbers.
