Do we need an adjustment?

[Kasz216]

Munkeh111 said:

crumas2 said:
I was under the impression that NPD was measuring sales to consumers in US-only, while VGChartz was measuring shipments from manufacturers for the Americas (not just the US).

Why are some posters claiming the numbers should match? Isn't this comparing apples to oranges?

 

VGC should be NPD + 10%, but the Xbox is 100% higher on VGC, and the PS3 is about 20% lower

You are ignoring NPD's margin of error as well.

When comparing two tracking sites together instead of a tracking site and the true number you need to remember they both have margins of error and can be off in different directions.

 

For example. Say i have 100 apples

Tracker A and his 10% error of margin says I have 110 apples

Tracker B and his 10% error of margin says I have 90 Apples.

Tracker A and Tracker B are now apart by more then 10%.

Famitsu and Mediacrate often differ by waaay more then 10%.