Examining personality requires both large scale and small scale research. Larger research studies may examine the factors that shape personality through the use of longitudinal and quasi experimental studies of people (Cozby, 2013; Ryckman, 2013). For example, John Bowlby (1983) studied the impact of attachment on personality and behavior by researching prison inmates' retrospective accounts of their childhoods. Smaller scale studies may also shed light on personality development, manifestation of a disorder, and the impact of administered treatment. Case study research tends to involve in-depth examination of a single or small group of clients. In a case study situation, a researcher may use self report, interviews, and observation in order to shed light on the case, make comparisons with other cases, and draw scientific conclusions (Ryckman, 2013). Similarly, clinical research is often used and may be a very valuable tool for understanding the impact of certain types of treatment. In clinical research, an experimental design may be used where two groups of participants receiving two different interventions are compared (Ryckman, 2013). Which of these methods produces the most valid information in the real world of personality research? Why?