Part I of this article provides factors for constructing frequently required intervals for a normal population and describes the situations in which each interval is applicable. The specific intervals considered are ones to contain with a high probability 1. All ofkfuture observations, 2. The mean ofkfuture observations, 3. A specified proportion of the population, 4. The population mean, 5. The standard deviation ofkfuture observations, 6. The population standard deviation. It is hoped that this article, by providing a side-by-side comparison of a variety of statistical intervals, will promote the construction of correct intervals.