For experiments in which the response is a time to failure or time to event, the response often needs to be transformed to a more useful scale, typically by taking the log of the response, or...

For experiments in which the response is a time to failure or time to event, the response often needs to be transformed to a more useful scale, typically by taking the log of the response, or sometimes by taking the inverse. For this experiment, log scale can be shown to be appropriate Fit the full second-order mean function (5.12) to these data using log(Life) as the response. Find the fitted equation, and obtain tests for the quadratic and interaction regressors.