quickrick said:
nemo37 said:
That's not how a ranking system (what Amazon uses) works. Rankings just tell you how far one item is from another NOT what the measurement of the distance between them is. Here is an example:
Console A is #1
Console B is #2
Console C is #3
Console D is # 4
Based on the above, all I can say is that Console A sold more than Console B, C, and D but I cannot say by how much. Nor can I say that Console D+C will outsell B (again because we don't know the distance from rank #2 to rank #3 nor do we know the distance from rank #3 and rank #4).
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meaning its useless.
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LOL...no. Amazon still provides lots of information on ranking of products sold online and overall movements between products; you just cannot use it to make statements regarding specific sales numbers. Granted interval/ratio data (data with specified measurement) gives you far more information, ranked data is still an invaluable source for seeing generally how products are doing against each other (in general). Now how predictive (ie useful) Amazon is with regards to overall ranking of sales requires us to employ a correlational analysis of the Amazon rankings with say, NPD, data.