Anecdotal evidence

Sometimes we hear the term ‘anecdotal evidence’ which is ‘evidence’ based on individuals’ own views and experiences. Is it really evidence? No – have a think about why.

The reason I bring it up is that over the week or so before half term I noticed what I thought was a big increase in the number of students off sick. I also noticed quite a few soldiering on in school with runny noses and tired faces. It felt like an outbreak and I diligently washed my hands as often as possible (teachers always get ill at the start of holidays, or is that just anecdotal evidence too?!).

But was this evidence of a flu outbreak? Almost certainly not. Although there were several absences, I couldn’t say for sure how many days students were off for and a genuine case of flu would result in several days from school. Perhaps it was just coincidence that alot of my students were off sick and this wasn’t the case in other classes? In fact when I look at our school data, although there was an increase in absences due to illnesses, it was less than the number reported before the Christmas holidays and was also decreasing slightly just before this half term.

So this highlights the importance of carefully collecting data in order to answer scientific questions and not to rely on people’s opnions. On the other hand, in an investigation such as this the experiences and information from students and staff in schools can help shed light on patterns in the absence data which could not be done by the scientists alone.

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One Response to Anecdotal evidence

  1. Dr Rob says:

    Thanks very much for this thoughtful lab log. Back in early Nov I wondered whether we were about to see the start of the flu season as nearly everyone in my office (including me eventually, despite the hand washing!) came down with some kind of respiratory illness. There was no flu peak at that time and the data made it clear that my anecdotal experience was wrong.

    Occasionally anecdotal evidence does turn out to be correct, particularly when the situation being observed is distinctive, as can sometimes be the case with unusual side effects from drugs. An historical example of this is the clinicians who first observed and raised concerns about thalidomide as the potential cause for birth defects in the children of women who had taken the drug as a treatment for morning sickness. These fortunately rare and urgent examples aside, it’s absolutely crucial to collect systematic and rigorous data in order to thoroughly examine the research questions we might have initially got from anecdotal observations. Without this, chance, and the biases we introduce through these small observations, can quickly get in the way truth.

    The first hand experiences students and staff can provide into this data analysis are also extremely helpful as they not only put the data in context, but they also bring it to life in a way that is often forgotten by researchers like myself who are sat in front of computers analysing data for most of the day…

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