Take into account that the confidence interval is given by:
[tex]\mu\pm Z\cdot\frac{s}{\sqrt[]{n}}[/tex]where
μ: mean = 18.2
Z: z-value for 95% confidence = 1.96
s = 18.2
n: sample = 86
Replace the previous values into the confidence interval formula:
[tex]\begin{gathered} 18.2+1.96\cdot\frac{18.2}{\sqrt[]{86}} \\ 18.2\pm3.85 \end{gathered}[/tex]Hence, the confidence interval is:
CI = (18.2 - 3.85 , 18.2 + 3.85) = (14.35 , 22.05)
Rounded to the nearest whole number the confidence interval is:
CI = (14 , 22)
