Foot drop Common Causes. Introduction: This information shows the various causes of Foot drop, and how common these diseases or conditions are in the general population. This is not a direct indication as to how commonly these diseases are the actual cause of Foot drop, but gives a relative idea as to how frequent these diseases are seen overall.
Variability refers to how spread out a group of data is. The common measures of variability are the range, IQR, variance, and standard deviation. Measures of variability are descriptive statistics, which means they can only be used to describe the study data.
Variance in itself is an excellent measure of variability and range, as a larger variance reflects a greater spread in the underlying data. The standard deviation is simply the square root of the variance. Squaring the differences between each point and the mean avoids the issue of negative differences for values below the mean, but it means the variance is no longer in the same unit of measure as the original data.