This edition: Confidence Intervals
Confidence intervals are something we see in the news almost daily, most frequently as polling results. They are the most commonly reported statistical results. Whether it involves who will win the next race for governor or what percentage of the population favors off shore drilling, the polls invariably report a percentage plus or minus some number. That range is the confidence interval, the subject of this lesson. It tells viewers the range of accuracy for that poll; in other words, by how much the results may be off. If the numbers in a poll are close and fall within this range, you know that the race or debate is not over.
This lesson gives you the statistical background to fully understand how these numbers are calculated, what the numbers mean and how they help statisticians to be confident about the results they report.