Order effect in interactive information retrieval evaluation: an empirical study

The purpose of this paper is to report a study of order effect in interactive information retrieval (IIR) studies. The phenomenon of order effect is well-known, and it is the main reason why searches are permuted (counter-balanced) between test participants in IIR studies. However, the phenomenon is not yet fully understood or investigated in relation to IIR; hence the objective is to increase the knowledge of this phenomenon in the context of IIR as it has implications for test design of IIR studies.

Order effect is studied via partly a literature review and partly an empirical IIR study. The empirical IIR study is designed as a classic between-groups design. The IIR search behaviour was logged and complementary post-search interviews were conducted.

The order effect between groups and within search tasks were measured against nine classic IIR performance parameters of search interaction behaviour. Order effect is seen with respect to three performance parameters (website changes, visit of webpages, and formulation of queries) shown by an increase in activity on the last performed search. Further the theories with respect to motivation, fatigue, and the good-subject effect shed light on how and why order effect may affect test participants’ IR system interaction and search behaviour.

Insight about order effect has implications for test design of IIR studies and hence the knowledge base generated on the basis of such studies. Due to the limited sample of 20 test participants (Library and Information Science (LIS) students) inference statistics is not applicable; hence conclusions can be drawn from this sample of test participants only.

Only few studies in LIS focus on order effect and none from the perspective of IIR.