Which of the following scenarios exemplifies a well-constructed operational definition in a psychological research study?
1
Researchers studying "stress" measure it by asking participants if they feel "stressed" on a scale from 1 to 10 at the end of each day.
2
Researchers investigating "intelligence" define it as the ability to solve complex mathematical problems without error.
3
Researchers examining "academic success" operationalize it as the average of the last three semesters' GPA scores of the participants.
4
Researchers exploring "happiness" define it as the frequency of smiling observed in individuals during a 30-minute interview