Neco 2019 Agricultural Science Question 18

A forest area of \(500\) ha is divided into five equal strata based on slope. Sample plots of \(0.1\) ha each are taken with the following results: - Stratum 1 (flat): 4 plots, mean volume \(120\ \text{m}^3\)/ha, variance \(400\). - Stratum 2 (gentle): 3 plots, mean \(150\ \text{m}^3\)/ha, variance \(625\). - Stratum 3 (moderate): 3 plots, mean \(180\ \text{m}^3\)/ha, variance \(900\). - Stratum 4 (steep): 2 plots, mean \(210\ \text{m}^3\)/ha, variance \(1225\). - Stratum 5 (very steep): 2 plots, mean \(240\ \text{m}^3\)/ha, variance \(1600\). Using stratified sampling, estimate the total timber volume for the whole forest and compute the 95 % confidence interval for the total volume. Use \(Z=1.96\).