Confidence Interval

Confidence intervals are a reasoned estimate about the true mean of a population based on a random sample. When looking at the mean (X) of a random sample of a population, most likely the mean of that sample will equal the true mean of the population ( ). However, the mean of the sample can be used as an estimate of the mean of the population. A confidence interval represents a range of values around the sample mean that likely include the true mean.

Confidence intervals are written with a percentage; what does this percentage represent?  It represents the level of confidence that the researcher has that the true mean is in the interval specified. The research sets the level of confidence desired, and the interval is adjusted accordingly. When considering a specific sample, the greater the level of confidence desired, the wider the confidence interval will be.

A Random Sample from this Population


In the previous menu, the Baby Weight Activity uses a confidence interval. To see the actual math used in finding a confidence interval, go to Confidence Interval Math.


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