Sampling error, the unspoken issue behind small number changes in the news
Ben Goldacre stresses the importance of taking account of “sampling variability” and confidence intervals.Key Concepts addressed:
Ben Goldacre, The Guardian, Saturday 20 August 2011
What do all these numbers mean? “‘Worrying’ jobless rise needs urgent action – Labour” was the BBC headline. They explained the problem in their own words: “The number of people out of work rose by 38,000 to 2.49 million in the three months to June, official figures show.”
Now, there are dozens of different ways to quantify the jobs market, and I’m not going to summarise them all here. The claimant count and the labour force survey are commonly used, and number of hours worked is informative too: you can fight among yourselves for which is best, and get distracted by party politics to your heart’s content. But in claiming that this figure for the number of people out of work has risen, the BBC is simply wrong.