SE = SD / √n
SD = standard deviation
n = sample size
For a proportion: SE = √[p(1 – p) / n]
For a mean: SE = s / √n
For a difference between two means: SE = √[(s1² / n1) + (s2² / n2)]
For a difference between two proportions: SE = √[p1(1 – p1) / n1 + p2(1 – p2) / n2]