Answer: The confidence interval would be (120.6, 159.4).
Step-by-step explanation:
Since we have given that
n = 200
mean = [tex]\bar{x}=140\ mm[/tex]
Standard deviation = [tex]\sigma=25\ mm[/tex]
At 95% confidence interval, z = 1.96
So, 95% confidence interval would be
[tex]\bar{x}\pm z\dfrac{\sigma}{\sqrt{n}}\\\\=140\pm 1.96\times \dfrac{140}{\sqrt{200}}\\\\=140\pm 19.40\\\\=(140-19.4,140+19.4)\\\\=(120.6,159.4)[/tex]
Hence, the confidence interval would be (120.6, 159.4).