A confidence interval, in statistics, refers to the probability that a population parameter will fall between two set values.

The confidence interval in this example is 95 percent, and the likelihood that the actual amount of plastic used is outside the estimated range is 5 percent.

Learn what Value at Risk is, what it indicates about a portfolio, its pros and cons, and how to calculate the VaR of a portfolio using Microsoft Excel.

Gelman himself makes the point most clearly, though, that a 95 percent probability that a confidence interval contains the mean refers to repeated sampling, not any one individual interval.