Researchers surveyed 19,183 U.S. physicians, asking for the information below. 

Location (region of the U.S.) income (dollars) employment status (private practice or an employee) benefits received (health insurance, liability coverage, etc.) specialty (cardiology, family medicine, radiology, etc.) time spent seeing patients per week (hours)

(a) Identify the population and the sample.

(b) Is the data collected qualitative, quantitative, or both? Explain your reasoning.

(c) Determine the level of measurement for each item above.

(d) Determine whether the study is an observational study or an experiment. Explain.