- Male college students, followed 3 years, Harvard University, USA, 1957-60
- N = 17
- Non Response:
- 37%: 9 dropouts, incomplete; about the same happiness distribution.
Multiple assesment methods
Mood diary kept 30 days and repeated interviews and tests during three years.
- Authors's Label
- Amount of sleep
- Our Classification
- Repeated direct question on number of hours sleep last night; during 6 weeks.