Ppt evaluation of information retrieval system

Submitted by
Somipam R. Shimray
Iii/semester dept. of LIS
Pondicherry University

INTRODUCTION
 Evaluation is a systematic determination of a subject's merit, worth
and significance, using criteria governed by a set of standards.
 It ascertain the degree of achievement in regard to the aim and
objectives and results of any such action that has been completed.
 Evaluation of information retrieval system measure which of the two
existing system perform better and try to assess how the level of
performance of a given can be improved.
 Lancaster state that evaluation of information retrieval system can be
justified by the following three issues:
 How well the system is satisfying its objectives
 How efficiently it is satisfying its objectives and
 Whether the system justified its existence.

PURPOSE OF EVALUATION
 The main purpose of the evaluation is to focus on the process of
implementation rather than on its impact.
 Evaluation studies also investigate the degree to which the state goals
have been achieved to which these can be achieved.
 To measure information retrieval effectiveness in the standard
way, we need a test collection consisting of three things:
 A document collection.
 A test suite of information needs, expressible as queries.
 A set of relevance judgments, standardly a binary assessment of
either relevant or non relevant for each query-document pair.

Swanson state seven purposes for evaluation:
 To assess a set of goals, a programme plan, or a design prior to
implementation.
 To determine whether and how well goals or performance
expectation are being fulfilled.
 To determine specific reasons for success and failure.
 To uncover principles underlying a successful programme.
 To explore technique for increasing programme effectiveness.
 To established a foundation of further research on the reason for
the relative success of alternative technique and
 To improve the means employed for attaining objectives or to
redefine sub goals or goals in view of research findings.

Keen give three major purpose of evaluation for an information
retrieval system:
 The need for measures with which to make merit comparisons
within a single test situation. In other words, evaluation studies
are conducted to compare the merits or demerits of two or more
system.
 The need for measure with which to make comparison between
results obtained in different test situation and
 The need for assessing the merit of a real-life system.

EVALUATION CRITERIA
 Evaluation of Information Retrieval can be conduct into two
different viewpoints.
 Managerial viewpoint: when evaluation is conducted from
managerial point of view it is called managerial oriented
evaluation.
 User viewpoint: when evaluation is conducted from the user point
of view it is called user-oriented evaluation study.

EVALUATION CRITERIA
Lancaster in 1971 proposed five Evaluation Criteria
 Coverage of the system
 Ability of the system to retrieve wanted items (i.e. recall).
 Ability of the system to avoid retrieval of unwanted items (i.e.
precision).
 The response time of the system and
 The amount of effort required by the user.

EVALUATION CRITERIA
 Recall
 Precision
 Fallout
 Generality

EVALUATION CRITERIA
Recall
 Recall is defined as the proportion of the total relevant documents
that is retrieved.
Number of relevant item retrieved
Recall=——————————————————————x 100
Total number of relevant items in the collection
 Example If there are 100 documents in a collection that are relevant
to a given query and 60 of these items are retrieved in a given
search, then the recall is state to be 60% in other words the system
has been able to retrieve 60% of the relevant items.

60
Recall= ———x 100
100
Recall= 60%
Total number of relevant items in the collection=100
Number of relevant item retrieved=60
Recall
Total no. of relevent
items
no. of relevent items

EVALUATION CRITERIA
Precision
 Precision is defined as the proportion of documents retrieved that is
relevant.
Number of relevant item retrieved
Precision=——————————————————x 100
Total number of items retrieved
 Example In a given search the system retrieves 80 items, out of
which 40 are relevant and 40 are non-relevant, the precision is 50%.

40
Precision= —————x 100
80
Precision= 50%
Total number of items retrieved=80
Number of relevant item retrieved=40
Precision
Total no. of relevent
items in the collection
Total no. of items
retrieved
No. of relevent items
retrieved

Recall-Precision matrix
R= [a/ (a+c)] x 100
P= [a/ (a+b)] x 100
Relevant Not-relevant Total
Retrieved a (hints) b (noise) a+b
Not-retrieved c (misses) d rejected c+d
Total a+c b+d a+b+c+d

EVALUATION CRITERIA
Fallout
 Fallout ratio is the proportion of non-relevant items that has been
retrieved in a given search.
Generality
 Generality ratio is the relevant items that have been retrieved in a
given search.

Retrieval Measure
Symbol Evaluation measure Formula Explanation
R Recall a/(a+c) Proportion of relevant
items retrieved
P Precision a/(a+b) Proportion of retrieved
item that are relevant
F Fallout b/(b+d) Proportion of non-relevant
items retrieved
G Generality (a+c)/(a+b+c+d) Proportion of relevant
items per query

LIMITATIONS OF RECALL AND
PRECISION
 Different users may want different levels of recall.
 A person going to prepare a state-of-the-art report on a topic would
like to have all the items available on the topics and therefore will go
for high recall.
 Where as a user wanting to know about a given topic will prefer to
have a few items and thus will not require a high recall.

OTHER EVALUATION CRITERIA
 Effectiveness
 Efficiency
 Usability
 Satisfaction
 Cost

Effectiveness
 Effectiveness means the level up to which the given system attained
its objectives.
 In an information retrieval system effectiveness may be measure of
how far it can retrieve relevant information while with-holding non-
relevant information.
Efficiency
 Efficiency means how economically the system is achieving its
objectives.
 In an information retrieval system efficiency can be measured be
factor such as cost.
 Cost include factor such as response time, time taken by the system
to provide an answer.

Usability
 Measure that embraces the interface through which the user interacts
with the system.
 Takes into account the user and their expectations, skills and
experiences.
Satisfaction
 Search task
 Search setting
 The searcher’s state contributes to quality and satisfaction judgments
in digital environments.
 Other perspectives on satisfaction are to be found in the service
quality and website quality literatures.

Cost
 Users may experience costs in terms of any payment that they need
to make for system or document access.
 Most significant cost is associated with the time that they spend in
searching a system.

CONCLUSION
 Evaluation is a systematic determination of a subject's merit, worth
and significance, using criteria governed by a set of standards.
 Effectiveness and efficiency are two basic parameter for measuring
the performance of system.
 Evaluation criteria
 Managerial viewpoint: when evaluation is conducted from
managerial point of view it is called managerial oriented
evaluation.
 User viewpoint: when evaluation is conducted from the user point
of view it is called user-oriented evaluation study.
 Recall, Precision, Fallout and Generality.

Ppt evaluation of information retrieval system

Ppt evaluation of information retrieval system

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Ppt evaluation of information retrieval system