Table 3.

Diversity of the filtered results in terms of mean number of trials in common with the first 20 displayed by ClinicalTrials.gov after the initial search. A small number of trials in common mean high diversity; the best system measures are reported in bold. Results are average over 100 distinct queries (“condition” AND “location”); for each query we applied different filters (all the combinations of available filtering values).

Filter Type	Number of Resulting Trials	Number of Trials Common to the Top 20 of the Initial Search
Original Search Results	544.13	n/a
Age only	358.86	12.62
Gender only	511.85	18.71
Study Type only	271.44	9.95
Age and Gender	337.39	11.79
Age and Study Type	179.28	6.29
Gender and Study Type	255.31	9.30
Age, Gender, and Study Type	168.80	5.88
eTACTS - 1 tag	142.62	4.56