How precise are our estimates? Confidence intervals
Abstract
To assess the precision of an estimate, compute its confidence interval. Use confidence intervals around all point estimates to understand the plausible range of the unknown population mean or proportion. Computing a confidence interval requires four things: an estimate of the mean, an estimate of the variability (derived from the sample standard deviation), the desired confidence level (typically 95%), and the sample size. Use the adjusted-Wald binomial confidence interval for binomial metrics such as completion rates. For satisfaction data using rating scales use the confidence intervals based on the t-distribution (which takes the sample size into account). The geometric ...
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