When would you choose FGD over interview?

You cannot ask everyone; you ask a sample.• Probability sampling: random, systematic, stratified (each stratum — e.g., ward, gender — fairly represented); supports statistical generalization.• Non-probability sampling: convenience, purposive (choose the knowledgeable — judges, survivors, officers), snowball (one respondent leads to the next; used for hidden populations). Sample size: enough for saturation (qualitative) or the confidence the design demands (quantitative). Always describe the sample honestly — who, how many, how chosen.