Practical evaluation guide

What is a baseline survey? Endline differences, design and cautions

An explanation of baseline and endline surveys, what to measure and when, comparable questions and practical cautions.

Compare before and after under consistent conditions

Even when a before-and-after difference is known, it cannot all be attributed to the program. Read the full explanation

Main takeaway

A baseline describes conditions before intervention or at observation start; an endline describes conditions at the end. Comparison requires indicators with the same meaning, consistent study conditions and target scope. Before-and-after differences cannot all be attributed to the program. [1]

After completion, programs often lack initial data when asked what changed from before. A baseline is starting-point information that cannot be recollected later.

Distributing a long questionnaire beforehand is not enough. Deciding which outcomes to compare when and for which decisions enables lower-burden research.

Create comparable baseline and endline records

Check the purpose and design of the research, comparability, and the limits of causal claims.

Roles of baseline and endline

A baseline measures starting conditions; an endline measures conditions at program completion or after a period. Consistent targets, definitions and similar conditions make differences easier to interpret.

For employment support, choose employment status, application behavior or other items with consistent definitions before and at completion. Plan a separate follow-up point if continuity after completion matters.

Roles of baseline and endline
TimepointMain purposeWhat to check
Before startingEstablish the starting pointTarget characteristics, current conditions, problems and existing behavior or knowledge
During implementationCheck emerging change and operationParticipation, initial change, attrition reasons and delivery quality
At completionCheck change and the next decisionOutcomes, satisfaction, intention to continue and improvements
After completionCheck sustainabilityEstablished behavior, maintained conditions and spillover effects
[1]

Design steps

First select questions and main changes to examine at completion. Rather than fixing item counts, check answerability, consistent definitions and sustainable recording.

Generally align baseline and endline question wording, options, scales and aggregation units. If changes are necessary, record them and explicitly report that simple comparison may not be possible.

  1. Decide evaluation questions and main outcomes
  2. Inventory data available before starting
  3. Minimize additional indicators and questions
  4. Decide targets, timing, methods and responsibilities
  5. Check that identical definitions can be used at completion
  6. Record missing data, attrition and external factors
[2]

Support comparability

Numbers with identical formats may measure different meanings. Changes in wording, question order or face-to-face, phone and online modes may affect responses. Where changes are necessary, check their effects and record comparison limitations.

Turnover in targets, attrition, seasonality and institutional changes also affect results. When change appears, consider explanations other than the program and supplement context through interviews or records as needed.

  • Align indicator definitions, units and response scales
  • Decide whether to follow the same individuals or compare whole groups
  • Retain initial and final response rates and missing-data reasons
  • Record major external factors and implementation-condition changes
  • Interpret quantitative differences with qualitative information
[2]

Avoid unwarranted causal claims

Before-and-after change need not arise from the program alone. Natural changes, other support or social conditions may influence results. Before-and-after comparison helps establish outcomes, but report it separately from demonstration of causal effects.

For stronger causal examination, consider comparison groups, multiple pre-intervention timepoints or contribution analysis. For small programs, practical decisions with explicit comparison limitations may be realistic.

  • Do not confuse before-and-after change with causal program effects
  • Check comparison groups and opportunities to examine alternatives
  • Distinguish individual changes from overall averages
  • Include data limitations in conclusions
[3]
Fictional example; not actual results

Report before-and-after differences among followed participants accurately

A fictional example for illustration: aggregate the 15 of 20 consultation recipients who answered the same questions at start and completion.

AggregationAt startAt completionInterpretation
Mean score for the same 15 people2.4 points3.1 pointsMean increase of 0.7 points among the same 15
5 people not followed upInitial records availableNo responseChange unknown
Study conditionsSame 5-point questionSame wording and response methodChanges in participants' self-assessments

What this example supports

Do not report the 15 people's differences as change for all 20. Avoid treating higher self-assessment as actual behavioral change or causal program effects.

Common errors in judgment

Treat means for 20 at start and 15 at completion as within-person change

How to revise: Separate matched-person analysis from aggregation of all respondents at each timepoint

Reason: Changes in respondent composition affect mean differences.

Improve question wording only at completion

How to revise: Where possible, test change effects and report differences in comparison conditions

Reason: This avoids confusing changes in instruments with changes in people.

Put it into practice next

Use the descriptive statistics worksheet to organize initial and final participant breakdowns and summaries

Frequently asked questions

Is a baseline survey always required before the program starts?

Pre-start data are easiest to compare, but existing administrative statistics, usage records or previous studies may substitute. Check their definitions and limitations.

When should an endline survey occur?

Align with when outcomes of interest arise. Consider delays, such as knowledge immediately after training, behavior after several months and conditions later still.

What if the same people cannot be followed?

Group comparisons at start and end are possible but cannot be read as individual change. Align target characteristics and interpret after checking differences in respondent composition.

References and checked sections

  1. Glossary of Key Terms in Evaluation and Results-Based Management for Sustainable Development (Second Edition)
    OECD · 2023
    Section consulted
    Baseline / Baseline study (main text, p.21) / End line (main text, p.30)
    How it relates to the text
    A basis for comparing pre-start and final conditions
    Source checked: (includes AI cross-checking)
  2. Best Practices for Survey Research
    American Association for Public Opinion Research
    Section consulted
    Planning Your Survey / How can I measure change over time? / What kinds of testing should I do before fielding a survey? / Analyzing and reporting the survey results
    How it relates to the text
    Questions fitting evaluation questions, consistent measurement conditions, pretesting, non-response and transparent reporting
    Source checked: (includes AI cross-checking)
  3. Is My NGO Having a Positive Impact?
    David Evans / Bruce Wydick(World Bank Development Impact) · 2016
    Section consulted
    Before and After / Beneficiaries and non-beneficiaries
    How it relates to the text
    Differences between NGO outcome measurement and causal effects, and limitations of before-and-after and participant/non-participant comparisons
    Source checked: (includes AI cross-checking)
Content updated: Source checked: (includes AI cross-checking)No documented human reviewIncludes fictional examplesEditorial policy and scope of checkingCite this pageReport a correction

How to cite this page

EvalCompass Editorial Team. “What is a baseline survey? Endline differences, design and cautions”. EvalCompass, updated 2026-10-14. https://evalcompass.jun-nakatani.com/en/guides/baseline-endline/
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Change history
  • — Distinguished original methodological sources from practical guidance and added specific fictional examples, judgment examples and next actions. Revised categorical claims about classification and measurement conditions.