Arun

Systematic Sampling

Systematic sampling selects elements at regular intervals from an ordered list.

Procedure

1. Compute sampling interval:
   $$ k = \frac{N}{n}$$
2. Choose a random start \( r \in [1, k] \)
3. Select units: $$r, r+k, r+2k, \ldots$$

Example: If \( N = 1000 \), \( n = 100 \), then \( k = 10 \). Select every 10th unit after a random start.

Caution

If there is hidden periodicity in data, systematic sampling can be biased.