4 4.1 A dataset on monthly stock market returns contains the following 4 observations. 9 7 5 1 REQUIRED: Calculate the sample mean, median, variance, standard deviation and coefficient of variation. If you were told that the skewness coefficient of the stock market returns is negative, what would you conclude about the shape of stock market returns' distribution? Illustrate your argument using a graph. (15%) 4.2 Explain the assumptions that underlie regression analysis and how residuals plots can be used to assess their validity (15%) (TOTAL 30%)