representation. n. 1. the act or an instance of representing or the state of being represented. 2. anything that represents, such as a verbal or pictorial portrait. 3. anything that is represented, such as an image brought clearly to mind.
The standard deviation and range are both measures of the spread of a data set. Each number tells us in its own way how spaced out the data are, as they are both a measure of variation. The range relies on a very simple formula of subtracting the minimum data value from the maximum.
The Standard Deviation is a measure of how spread out numbers are (read that page for details on how to calculate it). When we calculate the standard deviation we find that (generally): 68% of values are within. 1 standard deviation of the mean. 95% of values are within. 2 standard deviations of the mean.