Two sample T-tests for IR evaluation: Student or welch?

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    8 Citations (Scopus)

    Abstract

    There are two well-known versions of the t-test for comparing means from unpaired data: Student's t-test and Welch's t-test. While Welch's t-test does not assume homoscedasticity (i.e., equal variances), it involves approximations. A classical textbook recommendation would be to use Student's t-test if either the two sample sizes are similar or the two sample variances are similar, and to use Welch's t-test only when both of the above conditions are violated. However, a more recent recommendation seems to be to use Welch's t-test unconditionally. Using past data from both TREC and NTCIR, the present study demonstrates that the latter advice should not be followed blindly in the context of IR system evaluation. More specifically, our results suggest that if the sample sizes differ substantially and if the larger sample has a substantially larger variance, Welch's t-test may not be reliable.

    Original languageEnglish
    Title of host publicationSIGIR 2016 - Proceedings of the 39th International ACM SIGIR Conference on Research and Development in Information Retrieval
    PublisherAssociation for Computing Machinery, Inc
    Pages1045-1048
    Number of pages4
    ISBN (Electronic)9781450342902
    DOIs
    Publication statusPublished - 2016 Jul 7
    Event39th International ACM SIGIR Conference on Research and Development in Information Retrieval, SIGIR 2016 - Pisa, Italy
    Duration: 2016 Jul 172016 Jul 21

    Other

    Other39th International ACM SIGIR Conference on Research and Development in Information Retrieval, SIGIR 2016
    CountryItaly
    CityPisa
    Period16/7/1716/7/21

    Keywords

    • Statistical significance
    • Test collections
    • Topics
    • Variances

    ASJC Scopus subject areas

    • Information Systems
    • Software

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  • Cite this

    Sakai, T. (2016). Two sample T-tests for IR evaluation: Student or welch? In SIGIR 2016 - Proceedings of the 39th International ACM SIGIR Conference on Research and Development in Information Retrieval (pp. 1045-1048). Association for Computing Machinery, Inc. https://doi.org/10.1145/2911451.2914684