When the data is symmetrically distributed about the mean, the skewness is 0; The more dispersed the data on the right, the more biased it is to the right, and vice versa. If the mode is less than the median, the left side is more concentrated and the right side is more dispersed, then it is right deviation.
Left bias refers to the mode > average > median of data.
Right bias refers to the mode of data.