Approximation Error - How do you estimate error bounds?

When the confidence interval is known, the error bound may be approximated. The upper value point estimate or the difference between the upper and lower values divided by 2 are two ways to compute the error bound. When the population standard deviation is known, apply the normal distribution for means: EBM = zα2⋅σ√n. After that, the confidence interval would look like (ˋx − EBM, ˋx + EBM).