Final answer:
The type of sampling used by researchers studying anabolic steroid use, in which equal numbers of participants are selected from specified age groups, is Stratified sampling. Therefore, the correct option is b.
Step-by-step explanation:
The researchers studying the use of anabolic steroids have selected participants based on age intervals, taking an equal number of participants from three distinct age groups (20-29, 30-39, and 40-49). This sampling approach reflects a desire to obtain a representative subset from each stratum of the population, which, in this case, is defined by age groups. This method of sampling ensures that specific segments of the population are represented in the sample.
Stratified sampling is the technique being used here because it involves dividing the population into strata, or distinct subsets, and then randomly selecting samples from each stratum. In the described scenario, the strata are distinct age groups, and the researchers have randomly selected a fixed number of participants from each stratum to ensure that the age-based characteristics of the population are adequately represented in the study.
By choosing stratified sampling, the researchers can improve the accuracy and generalizability of their findings, allowing for more reliable extrapolation of the data to the entire population within those age ranges. It ensures a sufficient number of individuals from each age group is included to assess any age-related differences in the effects or usage patterns of anabolic steroids.