You want to calculate the variance of a series of past annual returns for IBM during the last 5 years. Which formula should you use? -VAR.P -VAR.S -STDEV -SQRT(st dev) Question 6 1 pts When we use 'expectation theory' to calculate the average, variance, and standard deviation of future returns for different securities and different scenarios that have varying probabilities of occurring, we can simply just use the =AVERAGE, -VAR.S, and STDEV.S functions in Excel. True O False