1.1 This practice covers guidance for the statistical analysis of laboratory data on the toxicity of chemicals or mixtures of chemicals to aquatic or terrestrial plants and animals. This practice applies only to the analysis of the data, after the test has been completed. All design concerns, such as the statement of the null hypothesis and its alternative, the choice of alpha and beta risks, the identification of experimental units, possible pseudo replication, randomization techniques, and the execution of the test are beyond the scope of this practice. This practice is not a textbook, nor does it replace consultation with a statistician. It assumes that the investigator recognizes the structure of his experimental design, has identified the experimental units that were used, and understands how the test was conducted. Given this information, the proper statistical analyses can be determined for the data.