Literature Searching

Document Sample
Literature Searching Powered By Docstoc
					How to do a Literature Search




           Ali Shareef
       University of Maine
            6/9/2010
                   Outline
•   The role of the literature review
•   Types of evidence
•   Formulating answerable questions
•   Sources of evidence
•   Search techniques
•   Optimal search strategies
•   Online tools
•   Evaluating your literature searching
  How to do a literature search
• The role of the literature review
    The role of the literature review - 1
•   Exposes main gaps in knowledge [and]
    identifies principal areas of dispute and
    uncertainty (Mays et al, 2001).
•   Helps identify general patterns to
    findings from multiple examples of
    research in the same area.
•   Juxtaposing studies with apparently
    conflicting findings helps explore
    explanations for discrepancies.
  The role of the literature review - 2

4. Helps define your terminology or
   identify variations in definitions
   used by researchers or practitioners.

5. Helps to identify appropriate
   research methodologies.

6. You can also identify validated
   scales and instruments.
   How to do a literature search
• The role of the literature review
• Types of evidence
      Some types of evidence
• Prediction – Models, case studies (single and
  multiple), documentary analysis
• Historical – documentary analysis, case studies,
  narratives
• Intervention – experimental studies
• Exploration – literature review, theory building,
  consensus processes
• Attitudes – psychological research
• Qualitative - using specific qualitative techniques
• Causation – observational studies (e.g. case
  control)
  How to do a literature search
• The role of the literature review
• Types of evidence
• Formulating answerable questions
Formulating answerable questions
• Translates “Aims” into achievable and
  focused tasks
• Helps to distinguish main from subsidiary
  questions
• Helps to identify the likely research
  designs to answer the research question
• Helps in constructing the literature search
                     Why?
• "Ask a poor question and you will get a poor
  review. A clear question also helps the reader
  rapidly assess whether the review is relevant to
  his or her own…practice". (Counsell, 1997)
• Clearly framed questions "guide much of the
  review process including strategies for locating
  and selecting studies or data, for critically
  appraising their relevance and validity, and for
  analysing variation among their results".
  (Cochrane Handbook)
         Some types of question
• Prediction – What is the likely result of X?
• Historical – How have we got from A to B?
• Intervention – Is doing Y better than doing Z?
• Exploration – What are the possible explanations for A?
• Attitudes – How do people feel about B?
• Causation – What are the likely causes of C?
• Measurement – What is the size of X, how often does it
  occur etc?
• Characterisation – How can we understand and specify W?
    How to do a literature search
•   The role of the literature review
•   Types of evidence
•   Formulating answerable questions
•   Sources of evidence
 Stages in the literature search
            process
• Focus your question
• Decide on the most appropriate sources
• Perform a scoping search by:
  –   Dividing your search into a series of „concepts‟
  –   Thinking of alternative terms for each concept
  –   Searching each concept separately
  –   Combining concepts using Boolean logic
  –   Limiting your search
• Revise your search, as necessary, and replicate
  in other sources
               Thoughts
• How credible are the sources?
• How relevant are the sources?
• Timely?
                                               General
                                   Citation      e.g.      Subject
  Registers                        indexes      ASSIA      specific
                                                          e.g. MEDLINE

                                                                    Evidence-
                                                                     based
Research
Councils
                           Reference          Databases
              Research        lists

                                                                    Contact with
                                                                    researchers/
                                                                    practitioners
                               SOURCES
                                                                                OPACs
    Handsearching                                            Grey
                                                          literature

                     Conference
                                      Pharmaceutical                           Databases
                     proceedings
                                         industry

                                                           Direct        Internet
              Published     Indexes                       contact
               copies
      How to do a literature search
•   The role of the literature review
•   Types of evidence
•   Formulating answerable questions
•   Sources of evidence
•   Search techniques
From: Etext on Health
Technology Assessment (HTA)
Information Resources. Chapter
4: Searching MEDLINE/PubMed
for Health Technology
Assessment Information by
Viveka Alton and Ione Auston.
http://www.nlm.nih.gov/nichsr/eh
ta/chapter4.html
   Take Home Message – 1
An optimal search will combine
natural language and controlled
    vocabulary approaches
                 Natural language
• Uses your own words and searches words & phrases
  (typically from the title, abstract & keyword fields) to
  retrieve records
• Potentially can search any field of a database
• Can be very precise (but there can be ambiguities e.g.
  Moderation [exam process] and Moderation [within
  reasonable limits] )
• Some problems:
   –   Plurals: e.g. child or children
   –   Different spellings: e.g. esthetic or aesthetic
   –   Different terminology: e.g. pavement or sidewalk
   –   Prefixes: prenatal, pre natal, pre-natal
    Database features to support
         natural language
• Truncation (e.g. *, $) used to search for
  different word stems and word endings
  – e.g. use comput* to find computer, computers,
    computed, computing, etc. (But comp* would find
    compost!)
• Wild cards (e.g. *, ?) used to search for spelling
  variants
  – e.g. use leuk*mia to find leukaemia or leukemia
• Proximity and adjacency operators (e.g. adj
  or near)
  – e.g. motor near2 accidents
        Controlled vocabulary
• Maps variations in terminology to a single
  “approved” word or phrase (e.g. Toyota, Rolls
  Royce, Mini, Ferrari etc. all mapped to
  “Automobiles”)
• Can demonstrate hierarchical or conceptual
  relationships (e.g. Europe-UK-England-
  Hampshire-Southampton)
• May not exist for new terms (e.g. “single
  currency”)
• May not map to a precise term (e.g. “teaching
  techniques” for “problem based learning”)
    Database features to support
       controlled vocabulary
• A Thesaurus (e.g. MeSH, ERIC) [NB.
  Opposite direction to Roget‟s Thesaurus –
  Many-to-One]
• Mapping
• Explode functions
• “See Under”, “Used For” and “See Also”
  references
   Take Home Message – 2
Getting unexpectedly few results
 can be worse than getting no
  results at all – “satisfied but
              inept”!
                       Explosions

Processors                          broad search
Embedded Systems
  Sensor Networks
         Power Saving Features
                                         specific
                                         search
Design
  RISC
  CISC
         Instruction Set
         Instruction Pipeline
         Wait States
                                    exploded
                Boolean - OR

Use to combine like terms or terms within the same concept



 CPU




                                                  Sensor
                                                  Networks


                CPU OR Sensor Networks
        Boolean - AND

Use to combine together different concepts


CPU



                                Sensor
                                Networks



   CPU AND Sensor Networks
            Boolean - NOT
      Use to exclude terms from your search




CPU



                                         Sensor
                                         Networks

            CPU NOT Sensor Networks
     Other search techniques
• Reference chaining: Follow up
  references from reference lists of relevant
  articles
• Hand searching: Identify key journals in
  your field and browse them cover to cover
• Relevance feedback: Look at subject
  indexing for a key reference and use to
  modify your search terms (Also “See
  Related Records” features)
    How to do a literature search
•   The role of the literature review
•   Types of evidence
•   Formulating answerable questions
•   Sources of evidence
•   Search techniques
•   Optimal search strategies
       What is an optimal search
               strategy?
“optimal permutations of search terms found in the
  titles, abstracts or the subject indexing of
  relevant articles that have been demonstrated to
  have a high correlation with study quality”
“pre-prepared search strategies, previously
  referred to as „search filters‟, „quality filters‟,
  „hedges‟ or „optimal search strategies‟…
  developed (and usually tested) for use with
  particular databases and/or search interfaces to
  retrieve specific types of evidence, study design
  or …information more effectively”
    How to do a literature search
•   The role of the literature review
•   Types of evidence
•   Formulating answerable questions
•   Sources of evidence
•   Search techniques
•   Optimal search strategies
•   Online Tools
              Online Tools

• Google
• Citeseer – http://citeseer.ist.psu.edu/cs
• UMaine Journal Databases
  – IEEE and ACM libraries available from any
    UMaine computer using UMaine IP
  – http://library.umaine.edu/default_idb.asp
    Click on Databases A-Z to see all databases.
                      Google
            http://www.google.com/help/features.html


• Using Boolean Expressions
  – AND (Default)
    • CPU AND PIC AND embedded systems
    • CPU PIC embedded systems
  – OR
    • CPU OR processors OR embedded systems
    • CPU | processors | embedded systesm
  – NOT
    •?
                    Google
• Using Boolean Expressions
  – NOT (minus sign)
     • CPU –PIC –embedded systems
     • Search for CPU while excluding PIC and
       embedded systems from results
• Exact strings
  – “CPU”, “New Mexico”, “Mexico”
• If the returned results is too large, use the
  “Search within results” option
                   Google
• Wildcards
  – „*‟/‟?‟ - Replace wildcard with any
    combination of characters
  – CP* or CPU* -- CP? or CPU?
• Site search – Restrict your search to a
  particular site
  – site:domain.com
  – Example: cluster computing site:*.edu
                  Google
• File types
  – filetype:pdf
  – Example: cluster computing filetype:pdf
                   Citeseer
                 http://citeseer.ist.psu.edu/cs



•   Displays references for each paper
•   Displays papers that cite the paper
•   Similar documents
•   Related documents
    How to do a literature search
•   The role of the literature review
•   Types of evidence
•   Formulating answerable questions
•   Sources of evidence
•   Search techniques
•   Optimal search strategies
•   Online tools
•   Evaluating your literature searching
Evaluating your search strategy
                Relevant         Not Relevant



Retrieved       Use to generate Eliminate terms
                additional      with poor yield
                search terms
Not Retrieved   Use reference    No further
                lists from key   action required
                articles to
                identify these
Take Home Message 3: Judge
not by what you have retrieved
  but by what you may have
           missed!
                 And finally …
• Documenting a search
  – Helps to avoid duplication,
    allows replication in future
  – e.g. date of search, sources
    searched, no. of hits, details
    of strategy, etc.
• Reference management
  – Reference Manager,
    EndNote, etc.
               References
• ESRC Research Methods Program
  – http://www.ccsr.ac.uk/methods/festival2004/
• Robert Gordon University
  – http://www.rgu.ac.uk/library/howto/page.cfm?
    pge=25989
The Great Internet Virtual Annual
  Scavenger Hunt (GIVASH)
  • Half-hour
  • Send me your responses by FC
    before the half-hour is up
  • Winner get “Geek of the Week”
    Certificate!
                              Questions
1.     What versions of Python does TOSSIM for TinyOS 2.0 use?
2.     What is Donald Worster‟s basic theme of the “Dust Bowl” according to
       Stanley Wayne Trimble?
3.     Under what kind of research does the question in 2 fall under?
4.     What kind of “systems” have been widely used in dental resins according
       to Suqing Shi?
     Hint: Paper proposes the use Benzodioxole-based coinitiators.
5.     What is the name of the building at the following address:
       “Via Fabio Filzi, 22, 20124 Milano, Italia 02 67651”
6.     What are the three fundamental types of Pointer processors in
       Synchronous Optical Networks (SONET)/Synchronous Digital Hierarchy
       Networks (SDH)?

				
DOCUMENT INFO