What kinds of sampling designs would be used for the following cases and why? Please, provide an explanation.
1.  A study to get a quick idea of the medical acceptability of a new aspirin substitute which cannot be dispensed over the counter without prescription.
2.  A study involving a sample of 325 students in a university where 2,000 students are enrolled (both with and without replacement).
3.  An investigation of the career salience of professionals in the fields of medicine, engineering, business, and law.
4.  The generalizability of the attitudes of blue-collar workers from a sample of 184 to the total population of 350 blue-collar workers in the entire factory of a particular company.