I want to do some bibliography research and I have a table with the average age of 10 samples. Each sample has different size. Also I don't have the SDfor every dataset info.
let (n1, x1), (n2,x2),.....(n10,x10) be the sample size and average respectively, of sample 1, sample 2 ,..... sample 10.
you can calculate the grand mean as X =(n1*x1 + n2*x2 +....+ n10*x10)/(n1+ n2 +...+ n10)
similarly, if s1^2, s2^2,.....s10^2 be the variances of samples 1, 2,...10 respectively, you can calculate the Pooled Variance S^2= [(n1-1)*s1^2 + (n2-1)*s2^2 +.... +(n10 -1)*s10^2)] / [(n1 - 1) +(n2 - 1) +.....+(n10 - 1)]
squared root of pooled variance gives the Pooled Std. Deviation.