A researcher is interested in studying the effect of having an MBA degree on consultants' mid-career salaries, so the researcher selects a random sample of mid-career consultants and sends each a questionnaire. The researcher finds that those consultants who earned MBA degrees at some point had, on average, salaries 23% greater than those who had not earned MBA degrees." in first answer choice, change "MBA caused" to "MBA degree causes. Which of the following is the most accurate description of this scenario? O The researcher conducted an experiment and can conclude that earning an MBA caused an increase in average mid-career salary. The researcher conducted a prospective observational study because the consultants were not randomly assigned to earn an MBA degree or not. The researcher can conclude that earning an MBA degree causes an increase in average mid-career salary. The researcher conducted a retrospective observational study because the consultants were not randomly assigned to earn an MBA degree or not. The researcher can conclude that, compared with not earning an MBA degree, earning an MBA degree is associated with a higher average mid-career salary. However, the researcher cannot conclude a causal relationship between those variables. The researcher conducted a prospective observational study because the consultants were not randomly assigned to earn an MBA degree or not. The researcher can conclude that, compared with not earning an MBA degree, earning an MBA degree is associated with a higher average mid-career salary. However, the researcher cannot conclude a causal relationship between those variables. O The researcher conducted an experiment but cannot conclude that earning an MBA degree causes an increase in average mid-career salary, because only observational studies can prove causal relationships.