packet that examine the potential effects that history can have on participants responses.

Questions related to age and numbers of years farming examine maturation.

 "External validity is the extent to which results of the study can be generalized

beyond the study" (de Vaus, 2001, p.28). It is important to differentiate between two

types of generalizability in case studies. Some researchers refer to statistical

generalizability when discussing external validity. Statistical generalizability is the

ability to generalize the findings of the research to a broader population than the sample.

Statistical generalizability can increase by using probability and random sampling. Case

studies sometimes do not aim to achieve statically generalizability. The findings from a

case study do not always offer explanations of phenomena to a population outside of

those who are studied. Rather, case studies focus on achieving theoretical

generalizability. Theoretical generalizability refers to the ability to generalize findings

from a study to a theory. The cases tell us about the effectiveness of the theory as an

explanation of the phenomena under study.

 Replication enhances the external validity of case studies (Yin, 2003). I used

multiple cases in this research both to achieve theoretical replication, by assigning groups

on maximum variability, and literal replication, by comparing cases within each group.

A major strength of the study is that it incorporated explanatory breadth by examining the

complex interactions between numerous variables. "Our ability to incorporate

complexity is a direct reflection of how well we understand and can explain the

phenomena we want to study" (M.E. Swisher, personal communications, November,

2005).

 Artificiality and sensitization are threats in this study. Some associate artificiality

with experimental designs. This can also be an issue with case studies and can affect