For a sample of 69 healthy trees the sample mean dyelayer de

For a sample of 69 healthy trees, the sample mean dye-layer density was 1.028, and the sample standard deviation was 0.163. Calculate a 95% CI for the true average dye-layer density for all such trees. Suppose the investigators had made a rough guess of 0.16 for the value of s before collecting data. What sample size would be necessary to obtain an interval width of 0.05 for a confidence level of 95%?

Solution