Sampling

Abdullah Al Mahmud

2026-09-28

What is Sampling

Population

  • Finite: people in Dhaka
  • Infinite: hairs in head, fish in pacific ocean, stars

Terms

  • Sample size
  • Parameter: Population characteristic (such as \(\sigma\))
  • Statistics: Sample characteristic (\(\bar x, sd\))

Census vs Sample Survey

Disadvantages of census:

  • Time
  • Cost
  • Quality
  • Accuracy
  • Multi-purpose

Steps of sample survey

  • Aim
  • Population
  • Sampling frame + unit
  • Type of data
  • Questionnaire
  • Method of data collection
  • Sampling method
  • Pilot survey
  • Field work
  • Data analysis

Samplig Methods

  • Probability/Random sampling
  • Non-probability sampling

Random sampling

  • Simple Random (SRS)
  • Systematic Sampling
  • Stratified Sampling
  • Cluster Sampling

SRS

  • Lottery method
  • Remainder approach
  • Quitient approach

Remainder approach

    1. N = 30 (digit d =2)
    1. N’ = Highest d-digit number = 90
    1. Choose a random number between 1 and N’ (90), say 65
    1. Divide by N (30) and select the Rth item (R = Remainder = 25)
    1. Repeat (3-4)

Systematic Sampling

  • Linear: \(k=\frac Nn\) is an integer
  • \(1 \le i \le k\)
  • If not divisible, \(k=\\approx \frac Nn\)

Question Bank

Practice Online

Practice Sampling MCQs interactively (with instant feedback): Stat & Prob Quiz

  • Pick Statistics II as subject and Sampling as chapter/topic.

Question Bank Archive

  • MCQ Bank — Sampling section starts at the relevant chapter.
  • CQ Bank — creative questions for Sampling.