Discarded Ipods: a sampling problem

Carrie asks:

If by any chance you’re still teaching kids to do surveys, we have a project we could REALLY use help on. . . . we’d love to have a survey of ipod users asking them how many ipods they have owned, how often they used each of them, and how long they lasted before dying. We’d then like to crunch that data to find the likelihood of the ipod dying at given intervals.

Matt writes,

I think this is indeed quite a difficult sampling problem. One idea is to take a sample of people who are actually listening to their ipod in a public place (like the subway). These people are often identifiable by the distinctive white ear plugs that come with the ipod. (As an aside, some marketing people suggest that the white ear plugs were key to the ipod’s success because it meant that each ipod user became a walking ad.) A problem with this approach is that it would over-sample people who listen to their ipods frequently. For example, I have an ipod that I rarely use and so I would be unlikely to be sampled. This over-sampling of ipods that are used frequently would probably lead to an overestimate of the failure rate. You could try to account for this over-sampling by weighting your results, but its unclear how accurate this would be.

If you have some money, you might be able to do a random-digit dial phone survey targeted to certain neighborhoods. I would guess that in some neighborhoods it may be the case that a random digit dial would be reasonably efficient at finding ipod owners. This random digit dial would not oversample people who use their ipods frequently, but it is more expensive and has problems with non-response (people who refuse to be in a phone survey or don’t have landlines).

A last idea would be to do some type of web-sample by buying ads on a site that ipod users visit. It looks like the itunes website does not accept ads and it also looks like buying the word “ipod” thought google adwords would be expensive. The other problem with a web survey is that its hard to tell who would click on your ad and actually complete the survey.

Also, I just had another idea, you could sample people leaving the apple store when they purchase ipods and then follow-up with them at regular intervals. The problem with this approach would be that you would not get any results for a while, but it would avoid many of the problems with the other approaches.

Any other thoughts?

6 thoughts on “Discarded Ipods: a sampling problem

  1. Andrew, that's a problem that companies have been trying to solve for a while. While I was at (insert name of Big 3 auto company here), the best answer was to get lists of buyers, and phone/mail them. It's a lot of work, and won't catch highly mobile people (like, say, college students/recent grads).

  2. Matt wrote:

    A problem with this approach is that it would over-sample people who listen to their ipods frequently. […] This over-sampling of ipods that are used frequently would probably lead to an overestimate of the failure rate.

    Why would it do that, if "time to failure" is measured as hours of play?

  3. I agree that you are not oversampling any population. The questions in the survey "how many hours a week do you listen to your ipod" and "for how long have you owned it," or some variation should give you an idea of hours of play, which is the important metric anyway. If you want to convert this to "months of use by average user," well, that data is also available. Of course, the estimates of hrs/wk would be somewhat inaccurate, but i'm guessing not much more so than in some of the other questions you are likely to ask. (i've seen people w/ broken audio devices that simply didn't have their headphones plugged in completely, and other trivial problems. otoh, i've seen devices in very sad shape that are considered 'operating' but at far substandard levels)

  4. A long shot: approach apple and see if they will share a sample of the customer database of iPod owners with you to contact for a survey. With cooperation, you might be able to take samples from different vintages, etc. Maybe they already know the answer…

  5. Given the problems, it might be nice to use the dreaded 'convenience sample'. Have each student ask 10 friends/acquaintances about iPod usage/breakage. Then proceed from there with analyses. The nice thing is that you've got clustering in the data, which can be demonstrated, analyzed, and accounted for.

  6. Matt wrote: "you could sample people leaving the apple store when they purchase ipods and then follow-up with them at regular intervals."

    I may be wrong, but I think most iPods are purchased at Wal-Mart or Best Buy. People who shop at Apple stores are more likely to be "Apple fans" who buy new iPods not because their old one failed, but because they want the latest model. Shoppers at Apple stores are probably more affluent as well.

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