Extreme values from skewed distributions [mathematics education]

Data from observations that cannot have negative values, such as pollution concentrations, traffic counts, or time intervals, are generally asymmetric with positive skew. If problems are assigned involving confidence limits, or the chances of rare events, with such skewed data, then the use of Gaussian-based statistics can result in substantial error. The magnitude of the error depends upon the mean value of the data expressed in units of the standard deviation. A set of curves is given which provides a method for correcting the Gaussian based tests, or at least for estimating the possible magnitude of the error.