The formula for interval estimate would be: μ = M ± Z(sM)
Where: μ is estimate
M is the mean
Z is the z value
(sM) is the standard error
μ = M ± Z(sM)
n = 200 rather than 50 (√200 = 2√50)
⇒ ME = (1/2) * 1.32 = .66
Using the formula above, plugging this in will give us: μ = 19.76 ± .66
= 19.76 ± .66 is the confidence interval or interval estimate