To choose a systematic sample you pick a random starting point and then take:

1. Systematic sampling walks through an ordered list at a fixed interval. 2. To choose a systematic sample, randomly select a starting point. 3. Then take every nth piece of data from a listing of the population. 4. Only the starting point is random, which is what distinguishes it from a simple random sample. _Source: OpenStax Introductory Statistics 2e (CC BY 4.0), Ch 1 'Sampling and Data', sections 1.1-1.4_