How Accurate Were the Pollsters in Flanders? You be the Judge
Last weekend, elections were held in Belgium. Not only for the European Parliament, but there were also federal and regional elections. As usual some people were quick to dismiss the polls. Isabel Albers, General Editor of De Tijd / L'Echo, made it clear on Twitter that she was not impressed: Some losing politicians made similar claims. Groen (the flemish Green party) co-chair Nadia Naji described her party's results as better than what the polls had predicted. Let's have a look at that claim: In 5 of the last 6 polls the true result was well within the usual confidence intervals (more on confidence intervals later). Only in the most recent one the true result was just outside of the 95% conidence interval, but notice that, to some extent, this is because the sample size in the last poll was 2000, which is higher than usual. As the blue line suggests, if you average the most recent polls, you would come very close to the actual election result. (More on poll averaging lat