DEMO: Spain: how to read poll averages

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A poll average is not a single poll but an estimate of voter sentiment from all published surveys. One poll has a sampling error of several percentage points, so the trend matters more than a single number.

On the Spain page you see the weighted average of the last three weeks, an arrow showing the change from the previous three weeks, and a chart with the dots of individual polls.

The shaded band around the line shows the uncertainty range. When the bands of two parties overlap, the gap between them is not statistically reliable.

Larger polls carry more weight in the average, and pollster deviations can be corrected by switching on the adjustment in the chart.

Read the full methodology on the Methodology page. Polls are not forecasts of election results.