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  EUROPA > European Commission > EuropeAid > Evaluation > Methodology > Basics > How?
Last updated: 04/01/2006

Methodological bases
Evaluation process (How?)


Data collection


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For the purpose of answering questions, the evaluation team collects data that are already available (secondary data) and applies data collection tools with a view to obtaining new information (primary data).

Existing information (secondary data)

To avoid duplicating efforts, running up unnecessary costs and tiring the informants, it is recommended wherever possible to rely on existing information (secondary data) such as:

  • Management and monitoring data
  • Studies and research relative to the field under consideration
  • Published statistical sources
  • Evaluation reports and their annexes

This information can be obtained at a lower cost. It can help to provide partial answers to some of the questions asked.

The most frequent difficulties

Even if the field data collection programme has been carefully prepared, the evaluation team may encounter unexpected problems during its fieldwork. The difficulties encountered most frequently concern:

  • Access to informants
  • Informants' unwillingness to cooperate
  • Cultural distance
  • Absence or weakness of information sought

Reliability of data collected

Evaluation surveys involve several kinds of risk. The reliability of the data collected can be threatened by biases such as:

  • Bias of confirmation
  • Bias of empathy
  • Self-censorship
  • Informants' strategy
  • Unrepresentative sample
  • Question-induced answers
  • Sample selection bias
  • Lack of statistical representativeness