🔢Explain Systematic Sampling.

🔢Explain Systematic Sampling.

Answer: In Systematic Sampling, units are selected at regular intervals after a random start.

If population size = N and sample size = n, then sampling interval k=N/n.

Select a random number r between 1 and k. The sample consists of:

r, r+k, r+2k, …, r+(n−1)k

Advantages:

• Simple and quick.

• Ensures even coverage across population.

• Suitable when list is arranged in an order (e.g., households in a street).

Disadvantages:

• Can lead to bias if population has periodic patterns related to kkk.

• Variance estimation is difficult without assumptions.

  
  

Numerical Example: Population N=1000, Sample size n=100. ⇒ k=10. If random start r=6, then selected units are: 6, 16, 26, 36, …, 996.

Cross Question:

👉 What are its advantages and disadvantages compared to SRS?

→ Easier to implement and often more precise if list is ordered logically. However, if periodicity exists, it may give biased results.

ISS Example: Used in industrial surveys — selecting every 10th factory in an industrial register.