Types of Sampling and Qualitative Sampling Methods: quick revision, 15 bites

Sampling: Studying a Few to Understand Many

Why study 1000 when 100 can tell the story?

**Sampling** means selecting a small part of a population to represent the whole. It saves time, money, and effort while still giving reliable insights.

Takeaway. A good sample mirrors the population, so findings can be generalised.

Two Big Families of Sampling

Probability vs non-probability — know the split.

Takeaway. Probability = random & representative; Non-probability = selective & insight-driven.

Types of Probability Sampling

Four random ways to pick a sample.

Takeaway. Probability methods give every unit a known, non-zero chance of selection.

Types of Non-Probability Sampling

When random isn't practical, choose wisely.

Takeaway. Non-probability sampling is fast and flexible but carries selection bias.

What is Qualitative Sampling?

Depth over numbers — that's qualitative.

**Qualitative sampling** focuses on selecting participants who can provide **rich, detailed, non-numerical information** about experiences, meanings, and behaviours.

Takeaway. Qualitative sampling prioritises information-rich cases over large numbers.

Purposive Sampling — The Researcher Decides

Hand-pick the right voices.

Takeaway. Purposive sampling = intentional selection for rich, relevant data.

Snowball Sampling — Participants Refer Others

One contact leads to many.

Takeaway. Snowball sampling grows like a rolling snowball through social networks.

Quota Sampling — Fixed Proportions

Fill the quota, match the population.

Takeaway. Quota sampling balances subgroups but selection within each is non-random.

Convenience Sampling — Easiest to Reach

Whoever is nearby gets picked.

Takeaway. Convenience sampling is quick but least representative.

Probability vs Qualitative Sampling — Quick Compare

Numbers vs narratives — pick your tool.

Takeaway. Use probability for breadth; use qualitative sampling for depth.

Don't Confuse Quota with Stratified

They look alike but differ in one key way.

Takeaway. Same structure, different selection rule — random vs non-random.

15-Mark Answer Framework

Structure your answer, score full marks.

Takeaway. Definition → Classification → Types with examples → Comparison → Conclusion.

Remember the 4 Qualitative Methods

P-S-Q-C: your qualitative toolkit.

Takeaway. P-S-Q-C = the four qualitative sampling methods.

Sampling in Real Life

From polls to product testing.

Takeaway. Different fields pick sampling methods based on their goal and constraints.

Watch Out for Sampling Bias

A bad sample ruins good research.

Takeaway. Always ask: does my sample truly reflect the population?