2. Using ar.yw() for small samples: The purpose of this exercise is to show that the residuals are not filtered properly, when using ar.yw() for a specific data set.

(i) Fit the model log(prostate cancer) ∼ colon cancer + colon cancer2 for males.

(ii) Use ar.yw() on the residuals to find values to build a filter.

(iii) Create the filtering matrix A.

(iv) Show A(residuals) is not white noise.

(v) Use ar.mle() on the residuals and create a filtering matrix B.

(vi) Show B(residuals) is close to white noise.