Skewness is a measure of distributional asymmetry. Conceptually, skewness describes which side of a distribution has a longer tail. If the long tail is on the right, then the skewness is rightward or positive; if the long tail is on the left, then the skewness is leftward or negative. Right skewness is common when a variable is bounded on the left but unbounded on the right. For example, durations (response time, time to failure) typically have right skewness since they cannot take values less than zero; many financial variables (income, wealth, prices) typically have right skewness since they rarely take values less than zero; and adult body weight has right skewness since most people are closer to the lower limit than to the upper limit of viable body weight.