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)?