Final answer:
The best method to obtain a representative sample is to randomly select from a list of all enrolled students, offering each individual an equal chance of selection and therefore representing the whole student body fairly.
Step-by-step explanation:
When considering which would be the BEST procedure for obtaining a representative sample of the students at your school, option d, sampling randomly from a list of all the students enrolled at your school, is the ideal method. This approach aligns with the concept of simple random sampling, where each student has an equal chance of being selected. By using a random number generator to choose students from the entire enrolled population, you avoid selection bias that could occur when only sampling from specific groups such as students in the student union, those in the library, or members of the student government. To enhance the representativeness of the sample, a stratified sampling technique could be incorporated, ensuring the sample reflects the proportion of students across different classifications such as freshman, sophomore, junior, or senior ranks if that data is relevant to the study.