How do you find the standard deviation? Struggling to get past that part

LDOONO'SU'l-PUJNiI NMHHHIiiIiIHHIIiI HOLDOONOWm-DUJNlIO 22 Portfolio Analysis a. Average Return b. Standard Deviation Year 2016 2017 2018 2019 Average Return Alternative 1 2 3 Alt 1 17.50% Historical Returns Asset F Asset G 16% 17% 17% 16% 18% 15% 19% 14% 17.50% 15.50% Investment 100% F 50% F and 50% G 50% F and 50% H Alt 2 Alt 3 16.50% 16.50% Asset H 14% 15% 16% 17% 15.50%