In Figure 2.4, the locations of objects (e.g., trees, mines, dwellings) in a study region are given by the centers of "+" symbols. The goal is to estimate the number of objects in the study region.
(a) A random sample without replacement of n = 10 units has been selected from the N = 100 units in the population. Units selected are indicated by
Shading in Figure 2.4. List the sample data. Use the sample to estimate the number of objects in the figure. Estimate the variance of your estimator.
(b) Repeat part (a), selecting another sample of size 10 by simple random sampling (without replacement) and making new estimates. Indicate the positions of the units of the samples on the sketch.
(c) Give the inclusion probability for the unit in the upper left-hand corner. How many possible samples are there? What is the probability of selecting the sample you obtained in part (a)?