Which of the following is a common measure used to quantify data spread?

The common measure used to quantify data spread refers to the statistical methods that assess how much the values in a data set differ from each other and from the central tendency of the data.

The median indicates the middle value of a data set when it is ordered, which is primarily a measure of central tendency rather than spread. Although it provides insight into the distribution of values, it is not a direct measure of spread like the others listed.

Standard deviation and variance both quantify how spread out the values in a data set are. Standard deviation gives us an idea of the average distance of each data point from the mean, providing a clear measure of variability. Variance, on the other hand, represents the average of the squared differences from the mean and is the square of the standard deviation. Both standard deviation and variance are essential in statistics for understanding the dispersion of data points.

Since the question asks for a common measure used to quantify data spread, option D is appropriate because it encompasses both variance and standard deviation, which are directly related to measuring spread, making it more comprehensive than any individual option, including the median. Thus, all three types of measures contribute valuable information, but standard deviation and variance are the most relevant for quantifying spread specifically.