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Evidence-Based Software Engineeringand Systematic ReviewsBarbara Kitchenham

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Agenda

The evidence-based paradigm Evidence-Based Software

Engineering (EBSE) Systematic Reviews

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The Evidence-Based Paradigm

Evidence-based medicine has changed research practices Medical researchers found

• Failure to organise existing medical research cost lives• Clinical judgement of experts worse than systematic

reviews Evidence-based paradigm adopted by many

other disciplines providing service to public Social policy Education Psychiatry

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Goal of EBSE

EBM: Integration of best research evidence with clinical expertise and patient values

EBSE: Adapted from Evidence-Based Medicine To provide the means by which current best evidence from

research can be integrated with practical experience and human values in the decision making process regarding the development and maintenance of software

Anticipated benefits Common goals for research groups Help for practitioners adopting new technologies Means to improve dependability Increase acceptability of software-intensive systems Input to certification process

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Practicing EBSE

1. Convert information need into answerable question

2. Track down best evidence3. Critically appraise evidence4. Integrate critical appraisal with SE

expertise and stakeholder requirements

5. Evaluate and improve above steps

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Systematic Reviews - 1/2

A systematic review is An overview of research studies that uses

explicit and reproducible methods Systematic reviews aim to synthesise

existing research Fairly (without bias) Rigorously (according to a defined

procedure) Openly (ensuring that the review procedure

is visible to other researchers)

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Systematic Reviews – 2/2

Support Evidence-based paradigm Start from a well-defined question

• Step 1

Define a repeatable strategy for searching the literature

• Step 2

Critically assess relevant literature• Step 3

Synthesise literature• Step 4 (but only partially)

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Advantages Provide information about effects of a

phenomenon across wide range of settings Essential for SE where we have sampling

problems Consistent results provide evidence that

phenomena are• Robust• Transferable

Inconsistent results• Allow sources of variation to be studied

Meta-analysis possible for quantitative studies

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Anticipated Benefits

Create a firm foundation for future research• Position your own research in the context of existing

research Close areas where no further research is

necessary Uncover areas where research is necessary Help the development of new theories

Identify common underlying trends Identify explanations for conflicting results

Should be a standard research methodology

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Disadvantages

Require more effort than informal reviews

Difficult for lone researchersStandards require two researchers

• Minimising individual bias

Incompatible with requirements for short papers

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Value of Systematic Reviews Can contradict “common knowledge”

Jørgensen and Moløkken reviewed surveys of project overruns

• Standish CHAOS report is out of step with other research

• May have used inappropriate methodology

Jørgensen reviewed evidence about expert opinion estimates

• No consistent support for view that models are better than human estimators

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Systematic Review ProcessDevelop Review Protocol

Validate Review ProtocolPlan Review

Conduct Review

Document Review

Synthesise Data

Write Review Report

Validate Report

Identify Relevant Research

Select Primary Studies

Extract Required Data

Assess Study Quality

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Developing the Protocol

Review protocol Specifies methods to be used for a

systematic review Predefined protocol

• Reduces researcher bias by reducing opportunity for

• Selection of papers driven by researcher expectations

• Changing the research question to fit the results of the searches

Good practice for any empirical study

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Protocol Contents -1/2

BackgroundRationale for survey

Research questionCritical to define this before starting

the researchStrategy used to search for primary

sources• Individual studies of the phenomenon of

interest

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Protocol Contents – 2/2 Strategy to find primary studies

Search terms, resources, databases, journals, conferences

Procedures for storing references How publication bias will be handled

• Grey literature• Direct approach to active researchers

How completeness will be determined• Useful to have the baseline paper to set start date

Selection Strategy Inclusion/exclusion criteria

• Handling multiple papers on one experiment

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Protocol Contents- 2/3

Quality assessment criteria Criteria used to evaluate quality of primary sources

Data extraction What data will be extracted from each primary source How to handle missing information How data reliability will be addressed

• Usually multiple reviewers Where data will be stored

Procedures for data synthesis Formats for summarising data Measures and analysis if meta-analysis is proposed

Should tested during protocol construction

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Research Question – 1/2 Question types for EBSE

Assessing the effect of an SE technology Assessing the frequency or rate of a project

development factor• E.g. Rate of project failures

Identifying cost and risk factors Identifying impact of technology on reliability,

performance, cost Possible to have more general questions for

other purposes Review of research in software engineering

(Glass, et al., 2002)

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Research Question – 2/2 Question structure

Population• People, projects types, applications types affected by

the intervention Intervention

• Software method, tool, procedure Outcomes

• Impact of technology in terms relevant to practitioners• Cost, quality, time to market

Experimental designs• Any constraints on type of primary studies to be

included

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Next steps are easy!?

Conduct the reviewEnact the protocol

• Expect further iterations of • Search strategy• Selection criteria• Data extraction

Record any deviations from protocol Document the Review

Using procedures defined in protocol

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Conclusions

Evidence-based approachRevolutionised medicineMay be relevant to SE

Systematic reviewsSupport the evidence-based approachValuable as a research tool

• Even if we don’t accept EBSE

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References

Australian National Health and Medical Research Council. How to review the evidence: systematic identification and review of the scientific literature, 2000. IBSN 186-4960329 .

Australian National Health and Medical Research Council. How to use the evidence: assessment and application of scientific evidence. February 2000, ISBN 0 642 43295 2.

Cochrane Collaboration. Cochrane Reviewers’ Handbook. Version 4.2.1. December 2003.

Glass, R.L., Vessey, I., Ramesh, V. Research in software engineering: an analysis of the literature. IST 44, 2002, pp491-506

Magne Jørgensen and Kjetil Moløkken. How large are Software Cost Overruns? Critical Comments on the Standish Group’s CHAOS Reports, http://www.simula.no/publication_one.php?publication_id=711, 2004.

Magne Jørgensen. A Review of Studies on Expert Estimation of Software Development Effort. Journal Systems and Software, Vol 70, Issues 1-2, 2004, pp 37-60.

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ReferencesKhan, Khalid, S., ter Riet, Gerben., Glanville, Julia., Sowden, Amanda, J. and Kleijnen, Jo. (eds) Undertaking Systematic Review of Research on Effectiveness. CRD’s Guidance for those Carrying Out or Commissioning Reviews. CRD Report Number 4 (2nd Edition), NHS Centre for Reviews and Dissemination, University of York, IBSN 1 900640 20 1, March 2001.

Kitchenham, Barbara. Procedures for Performing Systematic Reviews, Joint Technical Rreport, Keele University TR/SE-0401 and NICTA 0400011T.1, July 2004.

Pai, Madhukar, McCullovch, Michael, Gorman, Jennifer D., Pai, Nitika, Enanoria, Wayne, Kennedy, Gail, Tharyan, Prathap, Colford, John M. Jnr. Systematic reviews and meta-analysis: An illustrated, step-by-step guide. The National medical Journal of India, 17(2) 2004, pp 86-95.

Sackett, D.L., Straus, S.E., Richardson, W.S., Rosenberg, W., and Haynes, R.B. Evidence-Based Medicine: How to Practice and Teach EBM, Second Edition, Churchill Livingstone: Edinburgh, 2000.