Why ( or why not ) , when , and

© in this web service Cambridge University Press www.cambridge.org 21 The importance and prevalence of replication research varies greatly depending on the discipline and research area. In the so-called hard or pure sciences , for example, replication studies are common, and play an integral role in the process of testing and demonstrating the generalizability of crucial fi ndings. Gross ( 1997 ) notes two issues that support the need for replication studies in scientifi c disciplines. First, replication studies check the probability of error in the testing of null hypotheses, or the likelihood of a Type I or Type II error having been made. For instance, the probability for error in rejecting or accepting null hypotheses might have been affected by unrepresentative sampling or low numbers of participants. Thus, testing additional samples of the target population with the same methods provides supporting or contradictory evidence regarding the existence of a phenomenon. Second, replication studies are necessary to more effectively control for extraneous variables that might have confound ed the original fi ndings. As a result, replication contributes to increasing the explanatory power and generalizability of previous fi ndings in the “pure” sciences . In social sciences, such as sociology, psychology, and economics, as well as linguistics, conducting replication research contributes to “the essence of the scientifi c method” involving “observations that can be repeated and verifi ed by others” (American Psychological Association , 2010 : 4). Within social science research, some scholars believe a study is not complete until it has been replicated (Muma , 1993 : 927), yet results often prove diffi cult to reproduce. For example, according to Schneider , “a major problem in educational research is that investigators fi nd it diffi cult or are unable to replicate their work or that of their peers” (2004: 1472). This scarcity of replication and re-analysis of previous fi ndings undermines “the community’s ability to accumulate knowledge” (ibid.: 1473). Although calls have been made for more replications in many areas of the social sciences, including areas related to applied linguistics, such as speech and hearing research (Muma , 1993 ), research into how second languages are learned has only recently begun to be incorporated in replication studies. Why (or why not), when, and how to replicate research