Skewness reflects the degree of asymmetry of a distribution. If the distribution has a longer left tail, the function has negative skewness. Otherwise, it has positive skewness. A normal distribution is symmetric with skewness 0. In lognormal case, the curve has a long right tail so the skewness is positive.
is standard deviation
Missing data policy: Missing data is allowed in Skewness calculation. Minimum dataset size (12) is reinforced through standard deviation calculation. Total dataset size is the total numbers of valid dt.