A study is performed to discern if there is any difference in sitting heart rate between those who have two or less cups of coffee per day and those who have three or more cups per day. Subjects are selected at random based upon whether they drink two or less or three or more cups of coffee for each day and their heart rates measured at the same time each and every day for a period of 3 months.
I. What is the population?
II. What is the sample?
III. Is the study observational or experimental? Justify your answer.
IV. What are the variables?
V. For each of those variables, what level of measurement (nominal, ordinal, interval, or ratio) was used to obtain data from these variables?