Explain the probability and non-probability methods of sampling with their merits and demerits.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Open with definitions. Sampling is selecting a part (sample) of a population to study the whole. A sampling frame is the list from which the sample is drawn.
2 · Draw a chart of methods. [Chart: sampling → probability (simple random, systematic, stratified, cluster, multi-stage) | non-probability (convenience, purposive, quota, snowball)]
3 · Explain probability methods.
Simple random: equal chance, lottery.
Systematic: every kth unit.
Stratified: random from each stratum.
Cluster: whole groups at random.
Multi-stage: sampling in stages.
4 · Explain non-probability methods.
Convenience: whoever is available.
Purposive: chosen by judgement.
Quota: fixed numbers per group.
Snowball: referral chain.
5 · Give merits and demerits. For each method write one merit and one demerit, or draw them as a table.
6 · Nutrition example. Stratified random sample of girls by year of study for an anaemia survey; NFHS uses a stratified two-stage sample.
7 · Close in one line. Probability methods allow generalisation; non-probability methods are quick but biased.
Scoring tip: A table of methods with merits and demerits saves words and is easy for the examiner to mark.
