Response variables: are variables for the estimation of toxicity derived from any measured variables describing biomass by different methods of calculation.

In this method the test endpoint is inhibition of growth, which may be expressed by different response variables which are based on one or more measurement variables.

This should not be interpreted as a difference in sensitivity between the two response variables, simply that the values are different mathematically.

Measurement variables: are any type of variables which are measured to express the test endpoint using one ore more different response variables.

calculated response variables for each treatment replicate, with mean values and coefficient of variation for replicates

This Testing Method describes two response variables, as member countries have different preferences and regulatory needs.

In order for the test results to be acceptable in all member countries, the effects should be evaluated using both response variables (a) and (b) described below.

The response variables in the control and treatment group may be analysed using a statistical test to compare means, e.g. a Student't's t-test.

estimates of toxicity for response variables e.g. EC50, EC10, EC20 and associated confidence intervals.

For this method, growth rates and yield are response variables derived from measuring biomass directly or any of the surrogates mentioned.