Suppose, for example, that you want to know how many Australian children brush their teeth after breakfast. One way around this problem is to sample by surveying a small part of the total population. This technique is well established in science, but there are traps for the unwary. The sample must be unbiased, or random. This sounds easy, but in practice it might be quite difficult.
Sample size is also critical.
Australian mathematician Jane Watson investigated a claim made by a seafood company that 'Seven in ten men who frequently eat canned tuna, sardines, salmon, mackerel or kippers admit to being ambitious' - the implication being that a diet of fish increased ambitiousness. So the claim was true enough for the sample. But with such a small sample size it would be misleading to suggest that it represented the entire population of fish-eating men in the country. Deliberate misrepresentation For various reasons, governments, organisations and individuals don't always tell the truth - although they may be able to produce impressive numbers to justify their arguments. In the Australian tax debate, for example, all sides of politics can support their case with a vast array of numbers produced by economic models.