Simple Random Sampling Lecture 6 Section 2.5 Mon, Sep 6, 2004

Simple Random Sample Simple Random Sample of size n – A sample of size n chosen in such a way that all possible samples of size n have the same chance of being selected.

Selecting a Simple Random Sample Given a population of size N, Number the members from 1 to N. Use a random number generator (such as on a calculator) to generate n random integers from 1 to N. The sampling may be done with or without replacement. If the sampling is done without replacement, then repetitions should be discarded.

TI-83 – Selecting a Sample Suppose that the population size is N = 100. Press MATH. Use arrow keys to highlight PRB menu. Press 5 to select randInt (item #5). Enter randInt(1, 100) and press ENTER. A random number appears. Press ENTER repeatedly for more random numbers.

TI-83 – Setting the Seed Enter the desired seed, say, 33. Press STO. Press MATH, highlight PRB, select rand (item #1). Press ENTER. The seed is set to 33.

Example Example 2.14, p. 88 – Simple Random Sampling of Forest Sites.

Let’s Do It! Let’s do it! 2.4 – A Simple Random Sample of Companies. Let’s do it! 2.5 – Simple Random Sampling. Divide the class into two groups. Change “proportion of women” to “proportion of freshmen.”