Sample size for monitoring of toxic chemical sites.

The problem of determining sample size for environmental monitoring and assessment is considered. Hypothesis testing is discussed in general terms and in terms of monitoring toxic chemical sites. Competing risks of misclassification of sites are examined within the framework of statistics. Alpha and beta, the probability of making Type I and Type II errors, respectively, are illustrated in the context of environmental monitoring.Sample size formulas and tables are provided for comparing a mean to a standard mean, comparing two means, comparing a proportion to a standard proportion, and comparing two proportions. The formulas and tables consider the size of differences to be detected as well as the probability of Type I and Type II errors.