FURTHER INFORMATION ABOUT R-EXERCISE 2: Data: We will use the dataset "MASchools" included in the package "AER". The dataset contains data on test performance, school characteristics and student demographic backgrounds for school districts in Massachusetts. (The lectures use a similar dataset for schools in CA.) For the questions in this exercise, therefore, you should load the dataset "MASchools" via: > data("MASchools", package = "AER") There are alternative ways to load the data in R. In tutorial sessions for example, we loaded the package first and then loaded the data. R-tips: You might want to attach the dataset via: > attach(MASchools) You do not need to attach the dataset for this assessment. By attaching the dataset, however, you do not have to specify to which dataset the variables belong when you use them. For example, suppose you want to get summary statistics of the variable salary. Then, before attaching the dataset, you have to do this via > summary(MASchools$salary) But, once you attach the dataset "MASchools", you can do the same thing simply by > summary(salary) The R command attach() is useful when you work with many variables. When you do not need the dataset anymore, you can detach it via: > detach(MASchools)QUESTION 1 1 points Save Answer To learn the effect of student-teacher ratio on test scores, we use two variables: (1) student-teacher ratio (STR) and (2) 4th grade score (TestScore), which is the sum of math, English, and science in the dataset MASchool. What is the sample mean of the 4th grade score (one decimal place)? QUESTION 2 1 points Saved Estimate the population regression model: TestScore, = Bo + B1STR; + uj where E[ u;| STR;] = 0. What is the OLS estimate of the slope coefficient (two decimal places)? -1.72 QUESTION 3 1 points Saved Consider the estimated regression equation in Question 2. What is the robust standard error for the OLS estimate of the slope coefficient (two decimal places)? For this question, the standard error type in R has to be either "stata" or "HC1". 0.50 QUESTION 4 1 points Saved The minimum and maximum of STR are 11.40 and 27.00, respectively, in the data. Using the estimated regression equation in Questions 2 and 3, predict the difference in TestScores between the school district with STR = 11.40 and the school district with STR = 27.00. Report the difference in absolute value (two decimal places). 5.54