The skewness of a random variable was defined in Definition 4.4.1. Suppose that \({X_1},...,{X_n}\) form a random sample from a distribution \(F\). The sample skewness is defined as
\({M_3} = \frac{{\frac{1}{n}\sum\limits_{i = 1}^n {{{\left( {{X_i} - \bar X} \right)}^3}} }}{{{{\left( {\frac{1}{n}\sum\limits_{i = 1}^n {{{\left( {{X_i} - \bar X} \right)}^2}} } \right)}^{3/2}}}}\)
One might use \({M_3}\) as an estimator of the skewness \(\theta \) of the distribution F. The bootstrap can estimate the bias and standard deviation of the sample skewness as an estimator \(\theta \).
a. Prove that \({M_3}\) is the skewness of the sample distribution \({F_{{n^*}}}\)
b. Use the 1970 fish price data in Table 11.6 on page 707. Compute the sample skewness and then simulate 1000 bootstrap samples. Use the bootstrap samples to estimate the bias and standard deviation of the sample skewness.