In this exercise we will evaluate multivariate normality. Use the data in the file HW3-1.txt which is obtained from Forbes magazine and contains the world's 10 largest companies in 2005 (all amounts are in billions of $). Recall from class that if X ~ N p (????, ????), then (???? ????) ! ???? "# (???? ????) ~ ????$ % . a) Obtain a scatterplot matrix of all 3 variables. Compute the sample mean vector ????-, and the sample covariance matrix S