Why are so few lenses bought per DSLR? (Motivation of two polls)

Started Sep 29, 2013 | Discussions thread
OP merops Senior Member • Posts: 2,195
Re: Slow down.

roby17269 wrote:

I have no problem with your posts.


But have you considered that the population here may not be representative? I mean a lot of forum users here will probably have (had) more lenses than the average DSLR user.

Yes, I agree entirely that DPR readers are a biased sample of DSLR users. However, the main thing I'm interested in is the difference between the two values: lenses/camera bought, and lenses/camera available to use. The first of these values is what the industry can measure, but this measurement is being implicitly and mistakenly confused with the second value. As I posted, my values are 1.6 and 5, which is a huge difference. Also, it's possible for the first value to be less than one, whereas the second is only less than one if people own camera bodies for which they have no lenses at all.

However, I think there is still a problem: I want to be able to compare the (average) answer to the two polls. This can only be done if the samples for the two polls are not biased with respect to each other. This would be the case if people voted either in neither or both of the polls, but it seems that some people think that the polls are duplicates rather than asking different questions (that's kind of reasonable, because people are here for leisure reasons, and there's no rule that says they have to read stuff carefully), so only answer one. That's still OK, as long as the people who answer the first poll are not a biased sample in relation to those who answer the second poll. This issue wouldn't have arisen if DPR allowed two poll questions in one post. (So maybe I shouldn't have even tried asking this, but I was curious to know the answer.)

(The sort of data analyses I do for work makes me quite aware of the risks of biasing in sampling, and what conclusions you can and can't draw from data - hence my realisation that lenses/camera bought doesn't tell you whether people ever change the lens on their camera, and my interest in knowing how different the two values are.)

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