Welcome to Research Repository UCD
Research Repository UCD is a digital collection of open access scholarly research publications from University College Dublin. Research Repository UCD collects, preserves and makes freely available publications including peer-reviewed articles, working papers and conference papers created by UCD researchers. Where material has already been published it is made available subject to the open-access policies of the original publishers. This service is maintained by UCD Library.
- PublicationFocus groups versus individual interviews with children : A comparison of data(Routledge (Taylor & Francis), 2006)In recent years there has been an increase in the use of qualitative data collection techniques in research with children. Among the most common of these methods are focus groups and individual interviews. While many authors claim that focus groups have advantages over individual interviews, these claims have not been tested empirically with children. The present study reports on the use of focus groups and interviews to collect qualitative data from 116 children in three age groups, with mean ages of 8.4, 11.5 and 14.3 years. The children were randomly allocated to participate in either focus groups or individual interviews where they were presented with identical material and questions relating to their beliefs about peers with psychological disorders. In line with previous research, the interviews produced significantly more relevant and unique ideas about the causes of these disorders than the focus groups, but the latter gave rise to greater elaboration of ideas. The participating children showed no significant difference in their preference for one method over the other. Thus, whether to choose individual interviews or focus groups is likely to depend on the nature of the research question in any given study.
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- PublicationOptimal algorithms for ranked enumeration of answers to full conjunctive queries(ACM, 2020-05-01)We study ranked enumeration of join-query results according to very general orders defined by selective dioids. Our main contribution is a framework for ranked enumeration over a class of dynamic programming problems that generalizes seemingly different problems that had been studied in isolation. To this end, we extend classic algorithms that find the k-shortest paths in a weighted graph. For full conjunctive queries, including cyclic ones, our approach is optimal in terms of the time to return the top result and the delay between results. These optimality properties are derived for the widely used notion of data complexity, which treats query size as a constant. By performing a careful cost analysis, we are able to uncover a previously unknown tradeo ff between two incomparable enumeration approaches: one has lower complexity when the number of returned results is small, the other when the number is very large. We theoretically and empirically demonstrate the superiority of our techniques over batch algorithms, which produce the full result and then sort it. Our technique is not only faster for returning the first few results, but on some inputs beats the batch algorithm even when all results are produced.
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