What sampling technique –random, stratified, cluster, systematic, or convenience –was used? Explain. a. the first 30 people we see are asked a question b. all patients from 4 randomly selected hospitals are selected

In simple random sampling, each of the unit is population has equal chance of being selected in the sample.
Convenience sampling: In convenience sampling, the researchers select a sample from the section of the population that is most conveniently or easily available to them.
Voluntary response sampling: In voluntary response sampling, the respondents select themselves into the sample, by volunteering to take part in a study.
Stratified random sampling: In stratified random sampling, the population is sub-divided into homogeneous sub-groups. Then, a desired number of units is selected from each sub-group at random, to form a sample representative of the population.
Multi-stage sampling: In multi-stage sampling, the hierarchical structure of a large population is taken into account to collect samples in stages, by considering smaller sampling units at each subsequent stage.
Systematic sampling: In a systematic sample of size n, to be taken from a population of size N, the ratio k = N/n is first found; then, a random number is chosen between 1 and k, thereby selecting every kth population unit in the sample.
Cluster sampling: In cluster sampling, the population is subdivided into naturally occurring groups called clusters, such that each group can be treated as a representative of the population. Then, a desired number of those groups are selected at random, from the list of all groups, and every unit in the selected group is considered in the analysis.
a. In this case, first 30 people are asked a question.
In this case, the researcher sees first 300 people and these people are convenient to the researcher. Hence, he/she asked a question to the first 30 people.
Thus, it is a convenience sampling.
b. In this case, all patients from 4 randomly selected hospitals are selected.
Here, the population is all hospitals which is divided into some hospitals (clusters). Now, a desired number of hospitals, say 4 are selected and all patients of those hospitals are selected for the study.
Hence, it is a cluster sampling.