C H A P T E R 15 Observational Meth ods Jamie M. Ostro v and Emily J. Hart Abstract Systematic observational methods require clearly defined codes, structured sampling and recordin g procedures,and are subject to rigorous psychometric analysis. We review best practices in each of these areas with attention to the application of these methods for addressing empirical questions that quantitative researchers may posit. Special focus is placed on the selection of appropriate observational methods and coding systems as well as on the analysis of reliability and validity. The use of technology to facilitate the collection and analysis of observational data is discussed. Ethical considerations and future directions are raised. Key Words: Observation, observ er , time sampling , event sampling,participan t obse rvation, foca l participant sampling, semi-structur ed observations , scan sampling, interobserver reliability , Cohen’ s Kappa, observer drift, reactivity, remote audio -visual rec ording, computer -assisted observation al software Introduction Syst emat ic observ ationa l meth ods have been a common technique employed by psychologists stu dyi ng human and ani mal be hav ior since the inception of our field, and yet best practices for the use of obs erv ati onal ins tru ments (see T able 15.1) are often not known or adopted by researchers in our field. As such, the quality of observational research varies widely, and thus, it is our goal in the present chapter to review and explicitly define the standards of pra ctice for thi s imp ort ant met hod olog ica l too l in the psychological sciences. Bakeman and Gottman (1987) have previously defined observational meth- ods to include the a priori use of opera tional ly defi ned beh avi ora l cod es by obs erv ers who hav e achieved interobserver reliability. Importantly, the setting or context is not what defines a method as being systematic (P ellegrini, 2004). That is, system- atic observations may be conducted in the labora- tory, schools, workplace, public spaces and coded live or via recor dings/ transc ripts . Ther efore , hav- ing cle ar definit ions and sampli ng/r eco rd ing rul es as well as reliable codes delineates informal, unsystem- atic observation from systematic observation. We also distinguish between the use of nonsystematic field notes and other data collection techniques that are often used in qualitative studies by ethologists and educa tional pract itione rs in natura listi c contexts and only include a review and analysis of systematic observational methods (Pellegrini, Ostrov, Roseth, Solberg, & Dupuis, in press). Nonsystematic sampling techniques such as Ad libitum (i .e., ad li b) in wh ic h th ere are no a priori systematic sampling or recording rules are often used by researchers as a part of pilot testing and help to inform the development of system- atic observ ationa l coding syste ms (P elle grini, 20 04). Thus, ad lib sampling approaches are important to understand the context and nature of the behav- iors under stu dy , but they will not be dis cussed 285