19 February 2012

Making mince pies and MVD

Every year, in December, I embark on an epic quest to find mince pies. I have an addiction to these pastries, but also a particular dietary requirement which is not explicitly provided for by suppliers. I usually find a supply (and promptly buy a full gross before they can get away), but in the process I encounter the effects of what is, in the scheme of things, a trivial aspect of statistics in manufacturing to which I shall return below. When I last wrote[1] about this topic in Scientific Computing World, I was mostly concerned with the central rôle of data analysis in quality control. It plays a much wider and more diverse range of parts than that, however.

The fashion industry, for instance, is driven by statistical compromise. A dress maker uses over thirty metric descriptors, from height or waist circumference to the distance from neck to shoulder or armpit to hip. Most dresses, on the other hand, are bought on the basis of a single descriptor: a size, which in theory will always mean the same thing but in practice varies widely. In making this data reduction, a manufacturer needs to ensure that the best possible balance is struck between different customer shapes and perceptions. Most customers are going to find that a dress fits in one place, is too loose in another, and too tight in a third, but will only accept this within certain limits. Moving to a larger or smaller size will alleviate one problem while exacerbating another, and will also carry a psychological message about body shape. Getting the compromise wrong for a particular market will result in an exodus of customers to another manufacturer who has made shrewder decisions. These choices are heavily influenced by intuition and experience, but modelling on the basis of data analysis plays a large part, too. I know of one high street fashion supplier who regularly rents consulting time from a university department which maintains dedicated analytic software for the purpose. There are others which use in house statisticians running desktop software... [more]


Julie Heyward said...

I can never get your linked "more" pages to load. Perhaps the enigmatic "more" is a koan for me to ponder? [I'm on dial-up and I have stared studiously at "loading 2% for what I consider to be a polite amount of time].

Anyway, what I really hope this answers is whether 7.138kg of bananas was indeed the proper fit for Felix, or is it too loose in some places?

Julie Heyward said...

[follow-up: Felix was kind enough to send me a pdf version of his article (thank you!), which I find luxurious not only because of the special treatment, but because pdf files are much easier on my old eyes.]

Having now read and enjoyed the piece -- I'll try to keep it in mind while grousing to myself that manufacturers *always* cease making anything that I like, especially clothing -- the thing that comes to mind as being conceptually comparable is financial derivatives. Which are a sort of second level (or third level or fourth level ...) repackaging of assets, where what Felix's article seems to me to be about is second (or third ...) level repackaging of information.

[As if I know anything about this stuff ... ]

Felix said...

That (financial derivatives as informational repackaging metaphor) is a really interesting connection. I'll rip it off and make use of it!