Several important hidden properties about population variance and sample variance are highlighted. Very interesting, important queries are raised about the definition of the mean absolute deviation, the sample variance, and standard deviation. In. In addition, the close relationship between variance and the coefficient of variation is emphasized and highlighted. It is noted that these two measures of variation are functions of the same two quantities, the average of the squares and the square of the average of the data. A very important comment is raised about the definition of the mean absolute deviation.
Al-Saleh et al. (Tue,) studied this question.