Which of the following is the most frequently used measure of variation?

A) the mean
B) the range
C) the variance
D) the standard deviation
E) the median

The standard deviation is the most frequently used measure of variation as it provides a measure of how spread out the data is from the mean. The range only considers the difference between the highest and lowest values and can be influenced by outliers. The variance is also a measure of variation, but it is less frequently used than the standard deviation as it is harder to interpret and is in squared units. The mean and median are measures of central tendency, not variation.