To gather data on a 1200 -acre pine forest in Louisiana, the...

To gather data on a 1200 -acre pine forest in Louisiana, the U.S. Forest Service laid a grid of 1410 equally spaced circular plots over a map of the forest. A ground survey visited a sample of $10 \%$ of these plots. ${ }^{13}$ (a) Explain how you would use your calculator or Table D to choose an SRS of 141 plots. Your description should be clear enough for a classmate to carry out your plan. (b) Use your method from (a) to choose the first 3 plots.

To gather data on a 1200 -acre pine forest in Louisiana, the U.S. Forest Service laid a grid of 1410 equally spaced circular plots over a map of the forest. A ground survey visited a sample of $10 \%$ of these plots. ${ }^{13}$
(a) Explain how you would use your calculator or Table D to choose an SRS of 141 plots. Your description should be clear enough for a classmate to carry out your plan.
(b) Use your method from (a) to choose the first 3 plots.

Key Concepts

Use of Calculators or Random Number Tables

Calculators with built-in random number generators or random number tables (like Table D) are practical tools for selecting an SRS. These tools help generate a sequence of random numbers corresponding to the assigned numbers of the sampling frame units. The methodology involves selecting numbers from the generated sequence until the pre-determined sample size is obtained, ensuring that every unit has an equal chance of being chosen.

Sampling Frame

The sampling frame is the complete list or map of all units within the population from which the sample is drawn. In the context of the problem, the grid of 1410 equally spaced circular plots serves as the sampling frame. A well-defined sampling frame is essential for SRS because it allows for the assignment of unique identifiers to each unit, which is critical when using random selection methods.

Random Number Generation

Random number generation is a key tool in implementing SRS. Whether using a calculator's random function or a random number table like Table D, it enables you to assign numbers to each unit in the sampling frame and then select a subset according to randomly selected numbers. This process aids in ensuring that the selected sample is free from systematic bias.

Simple Random Sampling (SRS)

This concept refers to selecting a sample from a population in such a way that every possible sample of a given size has an equal probability of being chosen. It eliminates bias by ensuring that every individual unit (or plot, in this case) has an equal chance of inclusion, making SRS a cornerstone of representativeness in survey sampling.

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