I need help with 8.44 More on systematic sampling. Foresters were interested in

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I need help with 8.44

More on systematic sampling. Foresters were interested in studying a remote sensing measure of standing timber as an alternative to taking measurements on the ground. The study area was a 1200 acre pine forest in Louisiana on which the U.S. Forest Service first created a grid of 1410 equally spaced circular plots of 0.05 acre in size over a map of the forest. The ground survey then visited every 10th plot and took measurements of tree volume.^30 Assuming the plots are numbered from 1 to 1410, using the information in Exercise 8.43, explain how you will select a systematic sample of every 10th plot. Now choose a systematic random sample of 141 plots for the ground survey. If you use Table B, start at line 125. Why random digit dialing is common. The list of individuals from which a sample is actually selected is called the sampling frame. Ideally, the frame should list every individual in the population, but in practice this is often difficult. A frame that leaves out part of the population is a common source of under coverage.

Explanation / Answer

(a) Initially chose any random number between 1 and 1410

and then chose every 10th plot in regular intervals

For example if we have chosen randomly 6

The sample should have the following locations: 6,16,26,36.... 1406

(b) Here you will start with 125 and then chose 135,145... and so on once you reach 1405, you will again start from

5,15.. till you reach 125, which makes a sample size of 141

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