Generally, we use the standard deviation and not the variance to explain data. However, as a comparative measure, the standard deviation depends on the unit of measurement for it is not adept to use it across different measurement units. This means that we cannot or it would be difficult to compare different populations based on the standard deviation alone. Statisticians got around this disadvantage by defining the coefficient of variation, which measures the spread of the data relative to the mean in the form of a unit-less percentage, making it useful for comparing across different units of measurements and population

. .= 100% or 100%. Since the units of the mean and the variance are the same, when we divide them, their result is zero, hence, leaving the C.V. without units.

In-class exercise: Pace University's sushi bar sells spinners for students who want to fish at the Pond and then go to the bar to have the freshest sushi . The bar has eight different kinds of spinners and their prices in dollars are: 2.10 1.95 2.60 2.00 1.85 2.25 2.15 2.25.

a) Use a calculator with appropriate statistics keys to verify that for the Trading Post data, and $2.14 and $0.22.

b) Why did I ask you to calculate and instead of and s?

c) Which formula do you think your calculator uses, those of and , or those of and s?Justify

d) Compute the CV of prices for the spinners and explain the meaning of the result.