One-and-two-tailed tests.

Abstract

This chapter focuses on one- and two-tailed hypothesis tests. Two-tailed tests are used whenever the alternative hypothesis is that the population parameter is simply not equal to the hypothesized value, with no other specification. One-tailed tests are used when the alternative hypothesis is more specific, and when the hypothesis states that the population parameter is greater (or less, as appropriate) than the hypothesized value. The discussion in this chapter is presented specifically in terms of Normal distribution. For the Normal distribution and the t distribution presented in the chapter, the distributions are symmetric and the positions of the critical values for a two-tailed test are symmetrically positioned around the population parameters. The concept of a detection limit that allows an analyst to make a statement concerning the sensitivity of an analytical procedure is discussed.