Answer:

a. simple random, stratified, convenience

Simple Random Sampling;

• Simple random sampling, often abbreviated as SRS, is the purest and most robust probability sampling method. All members of a population have a known and equal probability of being selected into the sample. Several reputed polling agencies use the simple random sampling method to select a nationally representative sample for US Presidential approval rating polls.

Stratified Random Sampling;

• Stratified random sampling is a probability sampling method where individuals of the population are first divided into different groups or strata based on shared characteristics. Thereafter, the individuals are drawn randomly from each of the strata. For instance, the population of adults could be divided into smokers and nonsmokers before randomly selecting the subjects from each of the stratum.

Convenience Sampling:

• Convenience sampling is a non-probability sampling method wherein, as the name suggests, the sample is drawn from the population because of the ease and availability. A professor at a university may use his class of undergraduate students as a sample to study the effects of advertising on young adult perceptions of gender roles. Convenience samples don't often produce generalizable results but are useful in pilot testing the instrument of data collection.