how to use symsum for this problem

sym=symsum([i-Un]^2,i,1,s);

SD=(sym/n)^1/2;

Answer 1

[Torsten]

If you use symbolic variables, you should name them as such.

And you shouldn't name a variable "sym", especially if you do symbolic computations.

syms Un n i
symbolic_sum=symsum((i-Un)^2,i,1,n);
SD=simplify((symbolic_sum/n)^1/2)

SD = 

[Ashutosh]

thank you

[Walter Roberson]

Caution, ^1/2 is not ^(1/2)

syms Un n i
symbolic_sum=symsum((i-Un)^2,i,1,n);
SD=simplify((symbolic_sum/n)^(1/2))

SD =