Title: UsableStats: The Variability of a Sample
Headings: 
Introduction to Confidence Intervals :: The Variability of a Sample
Content: UsableStats: The Variability of a Sample















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Introduction to Confidence Intervals :: The Variability of a Sample
There are three areas that affect the width of a confidence interval. Sample Size
Confidence Level
Population Variability
As the sample size decreases, the confidence intervals get wider. As the confidence level increases the confidence intervals also get wider. Guess what else? As the variability of the population you're sampling from increases the confidence interval of your sample gets wider. So what is population variability? It's how much the individual data points differ from each other in the whole population. While populations are usually very large (like the millions of people in a country or thousands of patients at a hospital) they can also be much smaller.