Answer:
The answer is "(4.518, 5.182)"
Step-by-step explanation:
[tex]\sigma = 0.74[/tex]
The aveage porosity for a sample of [tex]n = 19[/tex] specimens is
[tex]\bar{x}=4.85[/tex]
Thus, the[tex]95\%[/tex] confidence interval for the true mean is
[tex]=\bar{x}\pm Z_{\frac{0.05}{2}} \frac{\sigma}{\sqrt{n}}\\\\=4.85\pm 1.96 \frac{0.74}{\sqrt{19}}\\\\=4.85\pm 0.332\\\\=(4.518, 5.182)[/tex]
Therefore, one can state that the true average porosity will lie between 4.518 and 5.182 with the 95\% confidence.
