Confidence intervals are in many ways a more satisfactory basis for statistical inference than hypothesis tests. This paper explains a simple method for using bootstrap resampling to derive confidence intervals. This method can be used for a wide variety of statistics - including the mean and median, the difference of two means or proportions, and correlation and regression coefficients. It can be implemented by an Excel spreadsheet, which is available to readers on the web. The rationale behind the method is transparent, and it relies on almost no sophisticated statistical concepts.