In this last equation, the variable log(len) is on the right side of the equation with an implied known regression coefficient equal to -1. A regressor with a known regression coefficient is called an offset, and most modern regression software allows you to include offsets in fitting a model. The difference between an offset and a regressor is that no coef- ficient will be estimated for the offset. Repeat Problem 10.2.2, but use log(rate) as the response and -log(len) as an offset. Is the analysis the same or different? Explain. 0.3 (Data file: mantel ) Using these "data" with a response Y and three regressors A , X,, and X, from Mantel (1970), apply the forward selection and backward elimination algorithms, using AIC as a criterion function. Also, find AIC and BIC for all possible models and compare results. Which appear to be the active regressors