intro.md
In precisely: Estimate Sample Size Based on Precision Rather than Power

This is a study planning tool to calculate sample size based on precision rather than power. Power calculations are focused on whether or not an estimate will be statistically significant; calculations of precision are based on the same principles as power calculation but turn the focus to the width of the confidence interval. Currently, you can calculate sample size for a desired precision, precision given a sample size, and sample size to have the upper limit of the confidence interval have a certain probability of being under a cut-off. The underlying R package, precisely, supports calculations for risk differences and ratios, rate differences and ratios, and odds ratios.