Chapter 7.2, Problem 4E

Answer questions 8.1.10, 8.1.11and 8.1.12 respectively

7.2.10 Researchers in the Hopkins Forest also count the number of maple trees (genus acer) in plots throughout the forest. The following is a histogram of the number of live maples in 1002 plots sampled over the past 20 years. The average number of maples per plot was 19.86 trees with a standard deviation of 23.65 trees. a. If we took the mean of a sample of eight plots, what would be the standard error of the mean? b. Using the central limit theorem, what is the probability that the mean of the eight would be within 1 standard error of the mean? c. Why might you think that the probability that you calculated in (b) might not be very accurate?     2. A normal population has mean 100 and variance 25. How large must the random sample be if you want the standard error of the sample average to be 1.5?

Answer questions 7.3.10 and 7.3.12 respectively  7.3.12. Suppose that two independent random samples (of size n1 and n2) from two normal distributions are available. Explain how you would estimate the standard error of the difference in sample means X1 − X2 with the bootstrap method.