Answer:
19.673
Step-by-step explanation:
Calculation
M = 19.8
Z = 2.58
sM = √(0.22)^2/20) = 0.05
μ = M ± Z(sM)
μ = 19.8 ± 2.58*0.05
μ = 19.8 ± 0.127
M = 19.8, 99% CI [19.673, 19.927].
You can be 99% confident that the population mean (μ) falls between 19.673 and 19.927.