Tuesday, 1 May 2012

Seeing is believing?

In a recent interview, Mary Beard recounted a Roman joke: "A guy meets another in the street and says: 'I thought you were dead.' The bloke says: 'Can't you see I'm alive?' The first replies: 'But the person who told me you were dead is more reliable than you.'" She used the joke (apparently considered hilarious all those centuries ago) to illustrate a point about changing cultures and the nature of evidence. But the question of evidence is just as important in our work today. When are verbal reports a reliable form of evidence, and when do you need more direct forms of evidence? What can you learn from web analytics or the device log of an infusion pump? What does observing people tell you, as against interviewing them? Etc.

In general, device logs of any kind should tell you what happened, over a large number of instances, but they can't tell you anything much about the circumstances or the causes (what people thought they were doing, or what context they were in). So they give you an idea of where problems might lie, but not really what those problems are; they give quantity, but not necessarily quality.

Conversely, interviews and observations can potentially give quality, but not quantity. They have greater explanatory power; interviews are good for finding out people's perceptions (e.g. of why they behave in certain ways), and observations will give insights into the contexts within which people do things and the circumstances surrounding actions. Interviews may overlook details that people consider unremarkable, while observations may catch those details but not explain them. And of course the questions that are asked or the way an observational study is conducted will determine what data is gathered.

As I type this, most of it seems very self-evident, and yet people often seem to choose inappropriate data gathering methods that don't reliably answer the questions posed. I'll use an example from a researcher I have great respect for, and who is undeniably a leader in the field: Ever since I first read it, I have been perplexed by Jim Reason's analysis of photocopier errors – not because it is inconsistent with other studies, but because it is based entirely on retrospective self-reports. But our memories of past events are highly selective. I make errors every day, as we all do (see errordiary for both mundane and bizarre examples), but the ones I can recall later are the ones that were most embarrassing, most costly. most amusing or otherwise memorable. So what confidence can we have in retrospective reports as a way of measuring error? I don't know. And I don't think that's an admission of failure on my part; it's a recognition that retrospective self-report is an unreliable way of gathering data about human error. And that remains a challenge: to match research questions and data gathering and analysis methods appropriately.

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