Evaluate a reliable way to measure it: stress

Consider you want to do a study in which class participation is an important variable that you need to quantify. How would you measure participation? Would you count the number of words spoken by each student, the number of seconds spoken, the time spent with their hands in the air or could you qualitatively measure their participation? Can you see the challenges in measuring this? A reliable measurement is one that is consistent. If everyone in the room is asked how cold it is, you would expect to see many different responses. However if you asked what the temperature is, you would expect to get identical responses (unless some were stating the temperature in Celsius instead of Fahrenheit). Assume you are a conducting a study that is measuring the variables Stress, Burnout and Happiness. Pick one of these variables and describe how you might determine a reliable way to measure it. Describe a specific example. Explain and defend the scale you would choose to use for this situation.