For random variable X, use the following statistics to calculate its coefficient of skewness based on central moments.
E(X) = 3.940
E(X2) = 21.466
skew(X) = E[(X - )3] = 6.008
Consider a function f which has three variables, x1, x2 and x3.
Identify which of the following gives a correct definition of a partial derivative of the function f.