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CHAPTER 6: Independent Groups Designs 211and it is, in fact, false, we are making a Type II error (Type I and Type II errorsare described more fully in Chapter 12). We would never make either of theseerrors if we could know for sure whether the null hypothesis was true or false.While being mindful of the possibility that data analysis can lead to incorrectdecisions, we must also remember that data analysis can and often does leadto correct decisions. The most important thing for researchers to remember isthat inferential statistics can never replace replication as the ultimate test of thereliability of an experimental outcome.ESTABLISHING THE EXTERNAL VALIDITY OF EXPERIMENTAL FINDINGS• The findings of an experiment have external validity when they can beapplied to other individuals, settings, and conditions beyond the scope ofthe specific experiment.• In some investigations (e.g., theory-testing), researchers may choose toemphasize internal validity over external validity; other researchers maychoose to increase external validity using sampling or replication.• Conducting field experiments is one way that researchers can increase theexternal validity of their research in real-world settings.• Partial replication is a useful method for establishing the external validityof research findings.• Researchers often seek to generalize results about conceptual relationshipsamong variables rather than specific conditions, manipulations, settings,and samples.As you learned in Chapter 4, external validity refers to the extent to whichfindings from a research study can be generalized to individuals, settings, andconditions beyond the scope of the specific study. A frequent criticism of highlycontrolled experiments is that they lack external validity; that is, the findingsobserved in a controlled laboratory experiment may describe what happensonly in that specific setting, with the specific conditions that were tested, andwith the specific individuals who participated. Consider again the video-gameexperiment in which college students played a race-car video game in a laboratorysetting. The laboratory setting is ideally suited for exercising control proceduresthat ensure the internal validity of an experiment. But do these findingshelp us understand violence and aggression in a natural setting? When a differenttype of exposure to violence is involved? When the people exposed toviolence are senior citizens? These are questions of external validity, and theyraise a more general question. If the findings of laboratory experiments are sospecific, what good are they to society?One answer to this question is a bit unsettling, at least initially. Mook (1983)argued that, when the purpose of an experiment is to test a specific hypothesisderived from a psychological theory, the question of external validity of thefindings is irrelevant. An experiment is often done to determine whether subjectscan be induced to behave in a certain way. The question whether subjectsdo behave that way in their natural environment is secondary to the questionraised in the experiment. The issue of the external validity of experiments is not