IRE An experiment: search strategy variations in SDI profiles chapter Lynn Evans Butterworth & Company Karen Sparck Jones All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, without the written permission of the copyright holder, application for which should be addressed to the Publishers. Such written permission must also be obtained before any part of this publication is stored in a retrieval system of any nature. r Experiment 293 If the tasks are interdependent then, on average, the sum of the task completion times for group A user statements should be less than for group B statements; and, the greater the interdependence the greater the difference in the total task times. It is assumed here that with a total of more than 50 user statements involved there is unlikely to be any bias between groups A and B caused by difference in subject matter or complexity. The average task completion times for groups A and B were as given in Table 14.1. TABLE 14.1 Users Average standard task completion times (mm) Average totals ti t2 t3 t4 t5 t6 t7 GroupA 34 13 11 11 7 9 3 88 GroupB 39 15 15 11 10 9 3 102 Not surprisingly the total of the average task completion times is lower for group A (88 mm) than for group B (102 mm), thus indicating some degree of interdependence of the tasks. No doubt also part of the difference is due to the effect of having to `re-understand' the user statement each time in group B. Alternatively it might be argued that groups A and B are not exactly similar or are not quite large enough to discount the effects of individual statement characteristics on the overall average task completion times. There is some support for this in that the average number of search terms is 44 for group A profiles and 50 for group B profiles. However the average standard task completion times for groups A and B are similar enough to encourage the conclusion that the degree of interdependence of the standard tasks is not so great as to invalidate the original division of the profile compilation process into the 7 standard tasks. Compilation times Combining the data for groups A and B the overall average standard task completion times (mm) were: t1=36, t2=14, 13=13, t4=11, t5=9, t6=9, and t7 =3 mm, which gave the average compilation times for the different search strategies as in Table 14.2. TABLE 14.2. Search strategy compilatioD times (average) Search strategy Average compilation times (mm) CT tI 36 TWC tl+t4 47 CTW tl+t4 47 CG tl+t2 50 GTWC t1+t2+t5+t7 62 Cow t1+t2+t5+t7 62 B tI+t2+t3 63 GwC t+t2+t5+t6 68 BW tl+t2+t3+t4 74