I need help with finding the standard deviation. I already have found the expected return of the economy. Please explain how you get the standard deviation. Thank you!

Use the following information for question 2 to question 3. Economic Conditions Probability Rate of Return 1 Strong economy, 0.69 16% no inflation Weak economy, 0.11 -5% above-average inflation No major change in economy 02 11% 2. What is the expected return of the economy? (Chapter 6. slide 11-12) Expected return =(.69.16) + 0.11 -05) + (2011) = .1104 + -.0055 +.022 = .1269 or 12.69% a. 9.18% b. 10.77% c. 11.98% d. 12.69% 13.11% e. 3. What is the standard deviation of the expected return? (Chapter 6, slide 14-16) 3. What is the standard deviation of the expected return? (Chapter 6, slide 14-16) (notes) .16 - 1269 = .0331 then .0331^2 = .00109561 then 69 * .00109561 = 7.559709 -.05 - 1269 = - 1769 then -.1769 2 = -03129361 then .11 - 03129361 -.0034422971 .11 - 1269 = - 0169 then -.0169^2 = -2.8561 then 2 -2.8561 - - 57122 7.559709 +-.0034422971 +- 57122 -6.985046703 a. 6.523% b. 7.612% c! 8.131% d. 9.026%