Question: Consider the example that was given, in which a reason-ably good fit was obtained by using a linear and a quadratic term. First graph the data. Does the quadratic model look reasonable based on the graph? Fit the quadratic model, as was done in, and then plot the standardized residuals against . Does this plot suggest adding a quadratic term, which is already in the model, or is there another type of term discussed in this chapter that might be expected to remove the trend in the plot? Add that term to the model and again plot the standardized residuals against . Does this plot still exhibit a trend? Use one or more variable selection methods (such as all possible regressions) to select a subset from these three candidate terms. What model do you recommend?