4. Important measures in exploratory data analysis are the skewness E(X - E(X)) 3 71 = Var(X) 3/2 and the kurtosis E(X - E(X) ) 4 72 Var(X)2 3. One way of estimating them is by using their empirical counterparts 1 = Vn EL,(Xi - X) 3 (EL,(X; - X) 2)3/2 and 12 = " Liz(Xi - X)4 (EL(Xi - X) 2)2 - 3, respectively. a) Write down two R functions myskewness and mykurtosis to calculate 71 and 72. b) In R load the library MASS and obtain the dataset nischools (Snijders and Bosker (1999) studies 2287 eighth-grade pupils (aged about 11) in 132 classes in 131 schools in the Netherlands). Use your functions to estimate 71 and 72 for the variable IQ (the verbal IQ score). library ("MASS") data ("nlschools") IQ