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EVALUATION in searching. IR systems Digital libraries Reference sources Web sources. Definition of evaluation. Dictionary: 1. assessment of value the act of considering or examining something in order to judge its value, quality, importance, extent, or condition In searching:

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EVALUATION in searching

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Evaluation in searching l.jpg

EVALUATION in searching

IR systems

Digital libraries

Reference sources

Web sources

© Tefko Saracevic

Definition of evaluation l.jpg

Definition of evaluation


1. assessment of value

the act of considering or examining something in order to judge its value, quality, importance, extent, or condition

In searching:

assessment of search results on basis of given criteria as related to users and use

criteria may be specified by users or derived from professional practice, other sources or standards

Results are judged & with them the whole process, including searcher & searching

© Tefko Saracevic

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Importance of evaluation

  • Integral part of searching

    • always there - wanted or not

      • no matter what user will in some way or other evaluate what obtained

    • could be informal or formal

  • Growing problem for all

    • information explosion makes finding “good” stuff very difficult

  • Formal evaluation part of professional job & skills

    • requires knowledge of evaluation criteria, measures, methods

    • more & more prized

© Tefko Saracevic

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Inf. need




Place of evaluation

© Tefko Saracevic

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General application

  • Evaluation (as discussed here) is applicable to results from a variety of information systems:

    • information retrieval (IR) systems, e.g. Dialog, LexisNexis …

    • sources included in digital libraries, e.g. Rutgers

    • reference services e.g. in libraries or commercial on the web

    • web sources e.g. as found on many domain sites

  • Many approaches, criteria, measures, methods are similar & can be adapted for specific source or information system

© Tefko Saracevic

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Broad context

Evaluating the role that an information system plays as related to:

  • SOCIETY - community, culture, discipline ...

  • INSTITUTION - university, organization, company ...

  • INDIVIDUALS - users & potential users (nonusers)

    Roles lead to broad, but hard questions as to what CONTEXT to choose for evaluation

© Tefko Saracevic

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Questions asked in different contexts

  • Social:

    • how well does an information system support social demands & roles?

      • hardest to evaluate

  • Institutional:

    • how well does it support institutional/organizational mission & objectives?

      • tied to objectives of institution

      • also hard to evaluate

  • Individual:

    • how well does it support inf. needs & activities of people?

      • most evaluations in this context

© Tefko Saracevic

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Approaches to evaluation

  • Many approaches exist

    • quantitative, qualitative …

    • effectiveness, efficiency ...

    • each has strong & weak points

  • Systems approach prevalent

    • Effectiveness: How well does a system perform that for which it was designed?

    • Evaluation related to objective(s)

    • Requires choices:

      • Which objective, function to evaluate?

© Tefko Saracevic

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Approaches … (cont.)

  • Economics approach:

    • Efficiency: at what costs?

    • Effort, time also are costs

    • Cost-effectiveness: cost for a given level of effectiveness

  • Ethnographic approach

    • practices, effects within an organization, community

    • learning & using practices & comparisons

© Tefko Saracevic

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Prevalent approach

  • System approach used in many different ways & purposes – in evaluation of:

    • inputs to system & contents

    • operations of a system

    • use of a system

    • outputs from a system

  • Also, in evaluation of search outputs for given user(s) and use

    • applied on the individual level

      • derived from assessments from users or their surrogates, e.g. searchers

    • this is what searchers do most often

    • this is what you will apply in your projects

© Tefko Saracevic

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Five basic requirements for system evaluation

Once a context is selected need to specify ALLfive:

1. Construct

  • A system, process, source

    • a given IR system, web site, digital library ...

    • what are you going to evaluate?

      2. Criteria

  • to reflect objective(s) of searching

    • e.g. relevance, utility, satisfaction, accuracy, completeness, time, costs …

    • on basis of what will you make judgments?

      3. Measure(s)

  • to reflect criteria in some quantity or quality

    • precision, recall, various Likert scales, $$$ ...

    • how are you going to express judgment?

© Tefko Saracevic

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Requirements … (cont.)

4. Measuring instrument

  • recording by users or user surrogates (e.g. you) on the measure

    • expressing if relevant or not, marking a scale, indicating cost

    • people are instruments – who will it be?

      5. Methodology

  • procedures for collecting & analyzing data

    • how are you going to get all this done?

    • Assemble the stuff to evaluate (construct)? Choose what criteria? Determine what measures to use to reflect the criteria? Establish who will judge and how will the judgment be done? How will you analyze results? Verify validity and reliability?

© Tefko Saracevic

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Requirements … (cont.)

  • Ironclad rule:

    No evaluation can proceed if not ALL five of these are specified!

  • Sometimes specification on some are informal & implied, but they are always there!

© Tefko Saracevic

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1. Constructs

  • In IR research: most done on test collections & test questions

    • Text Retrieval Conference - TREC

      • evaluation of algorithms, interactions

      • reported in research literature

  • In practice: on use & user level: mostly done on operational collections & systems, web sites

    • e.g. Dialog, LexisNexis, various files

      • evaluation, comparison of various contents, procedures, commands,

      • user proficiencies, characteristics

      • evaluation of interactions

      • reported in professional literature

© Tefko Saracevic

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2. Criteria

  • In IR: Relevance basic & most used criterion

    • related to the problem at hand

  • On user & use level: many other

    • utility, satisfaction, success, time, value, impact, ...

  • Web sources

    • those + quality, usability, penetration, accessibility ...

  • Digital libraries, web sites

    • those + usability

© Tefko Saracevic

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2. Criteria - relevance

  • Relevance as criterion

    • strengths:

      • intuitively understood, people know what it means

      • universally applied in information systems

    • weaknesses:

      • not static - changes dynamically, thus hard to pin down

      • tied to cognitive structure & situation of a user – possible disagreements

  • Relevance as area of study

    • basic notion in information science

    • many studies done about various aspects of relevance

  • Number of relevance types exist

    • indication of different relations

      • had to be specified which ones

  • © Tefko Saracevic

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    2. Criteria - usability

    • Increasingly used for web sites & digital libraries

    • General definition (ISO)

      “extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use”

    • Number of criteria

      • enhancing user performance

      • ease of operations

      • serving the intended purpose

      • learnability – how easy to learn, memorize?

      • losstness – how often got lost in using it?

      • satisfaction

      • and quite a few more

    © Tefko Saracevic

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    3. Measures

    • in IR: Precision & recall preferred (treated in Module 4)

      • based on relevance

      • could be two or more dimensions

        • e.g. relevant–not relevant; relevant–partially relevant–not relevant

    • Problem with recall

      • how to find what's relevant in a file?

        • e.g. estimate; broad & narrow searching or union of many outputs then comparison

    • On use & user level

      • Likert scales - semantic differentials

        • e.g. satisfaction on a scale of 1 to x (1=not satisfied, x=satisfied)

      • observational measures

        • e.g. overlap, consistency

    © Tefko Saracevic

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    • People used as instruments

      • they judge relevance, scale ...

    • But people who?

      • users, surrogates, analysts, domain experts, librarians ...

    • How do relevance, utility ... judges effect results?

      • who knows?

    • Reliability of judgments:

      • about 50 - 60% for experts

    © Tefko Saracevic

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    5. Methods

    • Includes design, procedures for observations, experiments, analysis of results

    • Challenges:

      • Validity? Reliability? Reality?

        • Collection - selection? size?

        • Request - generation?

        • Searching - conduct?

        • Results - obtaining? judging? feedback?

        • Analysis - conduct? tools?

        • Interpretation - warranted? generalizable?

    © Tefko Saracevic

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    Evaluation of web sources

    • Web is value neutral

      • it has everything from diamonds to trash

    • Thus evaluation becomes imperative

      • and a primary obligation & skill of professional searchers – you

      • continues & expands on evaluation standards & skills in library tradition

    • A number of criteria are used

      • most derived from traditional criteria, but modified for the web, others added

      • could be found on many library sites

        • librarians provide the public and colleagues with web evaluation tools and guidelines as part of their services

    © Tefko Saracevic

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    Criteria for evaluation of web & Dlib sources

    • What? Content

      • What subject(s), topic(s) covered?

      • Level? Depth? Exhaustively? Specificity? Organization?

      • Timeliness of content? Up-to-date? Revisions?

      • Accuracy?

    • Why? Intention

      • Purpose? Scope? Viewpoint?

    • For? Users, use

      • Intended audience?

      • What need satisfied?

      • Use intended or possible?

      • How appropriate?

    © Tefko Saracevic

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    criteria ...

    • Who done it? Authority

      • Author(s), institution, company, publisher, creator:

        • What authority? Reputation? Credibility? Trustworthiness? Refereeing?

        • Persistence? Will it be around?

        • Is it transparent who done it?

    • How? Treatment

      • Content treatment:

        • Readability? Style? Organization? Clarity?

      • Physical treatment:

        • Format? Layout? Legibility? Visualization?

      • Usability

    • Where? Access

      • How available? Accessible? Restrictions?

      • Links persistence, stability?

    © Tefko Saracevic

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    criteria ...

    • How? Functionality

      • Searching, navigation, browsing?

      • Feedback? Links?

      • Output: Organization? Features? Variations? Control?

    • How much? Effort, economics

      • Time, effort in learning it?

      • Time, effort in using it

      • Price? Total costs? Cost-benefits?

    • In comparison to? Wider world

      • Other similar sources?

        • where & how similar or better results may be obtained?

        • how do they compare?

    © Tefko Saracevic

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    Main criteria for web site evaluation

    © Tefko Saracevic

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    Evaluation:To what end?

    • To asses & then improve performance – MAIN POINT

      • to change searches & search results for better

    • To understand what went on

      • what went right, what wrong, what works, what doesn't & then change

    • To communicate with user

      • explain & get feedback

    • To gather data for best practices

      • conversely: eliminate or reduce bad ones

    • To keep your job

      • even more: to advance

    • To get satisfaction from job well done

    © Tefko Saracevic

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    • Evaluation is a complex task

      • but also an essential part of being an information professional

    • Traditional approaches & criteria still apply

      • but new ones added or adapted to satisfy new sources, & new methods of access & use

    • Evaluation skills in growing demand particularly because web is value neutral

    • Great professional skill to sell!

    © Tefko Saracevic

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    Evaluation perspectives - Rockwell

    © Tefko Saracevic

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    Evaluation perspectives

    © Tefko Saracevic

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    Evaluation perspective …

    © Tefko Saracevic

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    Possible rewards*

    * but don’t bet on it!

    © Tefko Saracevic

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