a) Categorize according to most descriptive or definitive category of research strategies (i.e., experiments, quasi-experiments, surveys, case-control studies, cohort studies, matched design, naturalistic observations, retrospective vs. prospective studies, longitudinal vs. cross-sectional studies, time-series, single-subject studies).

b) Recognize the features of the study which prompted your classification.

c) Recognize the IV, DV, and other variables, if appropriate.

d) Recognize and describe potential threats (up to 3) to internal validity.

e) Recognize and describe potential threats (up to 3) to external validity.

f) Recognize strategies that were employed to control for nuisance variables and minimize threats to valid inference making.

g) What additional strategies (up to 3) you would suggest that might raise the validity of the findings?

Please keep your answers brief.

Employment records were employed to recognize 100 men who had worked for the company in Los Angeles that manufactured chemicals employed as fire retardants. A second group of men, n=90, was identified who worked for two other companies in Los Angeles and had no exposure to chemicals. Evidence of primary thyroid dysfunction was found in four of exposed men; none of unexposed men showed evidence of thyroid dysfunction.