1 Refer to the American Mineralogist study of the evolution

1. Refer to the American Mineralogist study of the evolution of uranium minerals in the Earth’s crust. The researchers estimate that the trace amount of uranium x in reservoirs follows a uniform distribution ranging between 1 and 3 part per million (ppm). In a random sample of n = 60 reservoirs, let ¯x represent the sample mean amount of uranium.

a. Find E[x¯].

b. Find Var[x¯].

c. Describe the shape of the sampling distribution of ¯x. 2.

2. Refer to the Studies in Conflict & Terrorism (Vol. 29, 2006) analysis of recent incidents involving suicide terrorist attacks, data on the number of individual suicide bombings that occurred in each of 21 sampled Al Qaeda attack against the United States are reproduced in the table below. 1 1 2 1 2 4 1 1 1 1 2 3 4 5 1 1 1 2 2 2 1

a. Construct a confidence interval to estimate the true mean number of suicide bombings for all Al Qaeda attacks against the United States. Use = 0.1 to answer the question.

b. What assumption about the data must be true for the inferences to be valid?

Solution