The Centers for Disease Control and Prevention (CDCP) in Atlanta, Georgia, conducts an annual survey of the general health of the US population as part of its Behavioral Risk Factor Surveillance System. Using random-digit dialing, the CDCP telephones US citizens over 18 years of age and asks them the following four questions:

1. Is your health generally excellent, very good, good, fair, or poor?

2. How many days during the previous 30 days was your physical health not good because of injury or illness?

3. How many days during the previous 30 days was your mental health not good because of stress, depression, or emotional problems?

4. How many days during the previous 30 days did your physical or mental health prevent you from performing your usual activities?

Identify the parameter of interest for each question.