Shortcut Formula for Sample Variance and Standard Deviation (for grouped data) $2 n(Ef.xm)-(£8.Xm)2 n(n-1) S = Range Rule of Thumb A rough estimate of the standard deviation is S range 4 Example 8: Find the population mean, range, variance, and standard deviation for the following data: 10, 20, 12, 17, 16. Mean = X (X - mean) Range = (X - mean Total Variance Standard deviatio