In finance theory, standard deviation is used or considered as a measure of risk. This methodology can be applied to expected returns on a real estate investment. However, there are a number of assumptions underlying the application of the theory. Which one of the following assumptions is incorrect?

	a.	Standard deviation is a measure of volatility
	b.	The sample data set is representative of the population of outcomes
	c.	Data should be gathered in an unbiased way
	d.	Variations above the mean are weighted more heavily than those below