Measures of variability match-up There are multiple ways to refer to or describe a variance or a standard deviation of either a population or a sample. Likewise, each measure has multiple appropriate equations or symbols. The first table consists of alternative ways of referring to each of these measures. The second table consists of equations or symbols for each of these measures. Alternative Description a. Square root of the average squared distance from u b. Mean squared deviation from M c. Mean squared deviation from u d. Standard distance from M