# Australian Bureau of Statistics

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 Understanding statistics

Module 1: Producing Data

3. Sources of data > 3.1. Use of available data

i. Anecdotal evidence

Even though you might not think about it a lot, you often make decisions in your life based on experiences that you have had or on things that you have heard about. In such cases you are basing your decisions on anecdotal evidence.

Let's say a friend of yours claims that a particular brand of inexpensive shower cleaner is really good. Your friend explains that he simply sprayed it on the tiles, left it for 10 minutes, and when he came back the tiles were spotless - without him having scrubbed or done anything else! This anecdotal evidence is enough of a recommendation for you. You buy some and use it, thus testing the evidence for yourself.

Another example of anecdotal evidence occurs when we decide not to go to a particular area because we have heard that an isolated event such as an horrific crime has occurred there. However, there is an overwhelming body of evidence that we have a much greater chance of being seriously injured driving a car locally, and yet we do not hesitate to get in a car and drive somewhere.

 Scenario A friend of yours says he will never wear a seat-belt again. He explains that an acquaintance of his survived a car accident because she wasn't wearing a seat belt. The acquaintance flew through the windscreen, landed on a grassy bank and suffered minor injuries. Meanwhile the car burst into flames and was destroyed. You are not convinced by this story alone that it is a good idea to abandon wearing a seat-belt.

 Test your knowledge Question What were the researchers trying to find out? Select from the options provided below another way of collecting data that would be more convincing than this anecdotal evidence. a) Observe a busy street to see how many drivers involved in accidents are wearing seat belts. b) make up the data so it supports your friends view that seat belts are a waste of time. c) Conduct an experiment in which a number of drivers, half of which are wearing seat belts, drive into a brick wall. d) Examine a large number of accident reports to see whether survivors were wearing seat belts or not. Answer Click here for answers

The limitations of anecdotal evidence

The limitations of anecdotal evidence are that often the anecdotes are curious, peculiar or extraordinary and are not typical or representative. This causes them to stay in our memory, but it does not make them typical. This lack of representativeness means that you need to be careful when making conclusions about a much broader population from anecdotal evidence.

When to use anecdotal evidence

Despite its limitations, anecdotal evidence is important in some areas of research, such as case study research, where the emphasis might be on learning as much as you can about a specific situation and you have to depend on a person's own experience for information/data. Even in areas where anecdotal evidence is not considered valid or reliable for the type of study that you want to conduct, it can strongly suggest lines of research.