**Question:** All of the following are random sampling methods except

A. Convenience sampling
B. Stratified sampling
C. Quota sampling
D. Cluster sampling

**Core Concept:** Random sampling is a type of sampling technique in research where the selection of participants is done in a way that ensures equal chances for each member of the population to be included. This helps to minimize bias and increase the generalizability of the study results.

**Why the Correct Answer is Right:** Convenience sampling involves selecting participants based on their availability and accessibility at the time of study initiation. This method is not truly random and introduces bias into the study, making it not a true random sampling technique.

**Why Each Wrong Option is Incorrect:**

A. Convenience sampling: As explained above, convenience sampling introduces bias and is not a true random sampling technique.
B. Stratified sampling: This method involves dividing the population into subgroups (strata) based on certain characteristics and then randomly selecting participants within each stratum. This is a valid random sampling technique.
C. Quota sampling: Quota sampling involves selecting participants based on predetermined proportions of specific characteristics or groups within the population. It is not a random sampling technique because it is not truly random and introduces bias.
D. Cluster sampling: In cluster sampling, the study population is divided into clusters, and then random samples are taken from each cluster. This is a valid random sampling technique.

**Clinical Pearl / High-Yield Fact:** Cluster sampling allows researchers to study larger populations by sampling smaller parts (clusters) and then extrapolating the findings to the entire population. This method can be effective when studying large and geographically dispersed populations.

**Correct Answer:** Convenience sampling (Option A) is not a true random sampling technique.