Systematic Sampling Lecture 9 – Part 1 Sections 2.8 Wed, Jan 30, 2008

Systematic Sampling 1-in-k systematic sampling.

Systematic Sampling To determine k, divide the population size N by the desired sample size n. Let k = N/n (rounded off).

Systematic Sampling Then choose a random starting point from 1 to k. That is, choose a member at random from the first block of size k. From that starting point, count off every k th member and put them in the sample.

Example Suppose we want to select n = 5 members from a population of size N = 52. Compute k = 52/5  10. Use randInt(1, 10) to get a random integer from 1 to 10. Say we get 6. Then select members 6, 16, 26, 36, 46 to be in the sample.

The Sample Size Notice that, since 52/10 = 5.2, the sample size could end being either 5 or 6, depending on the starting point. Had the starting point been 2, then the sample would have been 2, 12, 22, 32, 42, 52 (6 members).