There are two kinds of problems, conceptual and application. The conceptual problem focuses on definition, notation, and formula. For this kind of problem, you are supposed to compute by hand (or basic arithmetic function in Excel or R), but not the function that directly shows the answer. Formula and working progress should be clearly shown. By default, all questions in the homework assignment are of this type. The application problem focuses on R application skill and output interpretation. This problem usually contains the phrase "use R....", or "according to the R output". For this kind of problem, you don't need to compute the results by hand. Instead, get the result from R and proceed. For instance, in the homework 1, problem 1-3 are conceptual problems, and problem 4 is application problem. For problems 1 to 3, you may use Excel or R to compute the residuals and sum of squares, means for the variables before compute the residual standard error. When computing the item, show the formula and detail and use the correct notation. You may not use the linear regression function, such as lm() to compute the numbers because the purpose of these problems is to get familiar with