Various data collection methods can be employed as part of an outcome and impact assessment. As a rule, one can distinguish between qualitative and quantitative collection methods. Aside from the choice of data collection methods, it is important to consider, as a second step, whether all or only a part of the affected units, target groups or cases are represented in the data collection for the impact assessment (unit of analysis). Furthermore, it is important to conduct a critical review of the quality of the collected data (data quality).
Package of methods
It is normal in contemporary research routine to use a combination of qualitative and quantitative methods in order to benefit from the advantages of both methods. This is what people call a package of methods, or triangulation. The usefulness of a combination of qualitative and quantitative methods is undisputed and has become regulation practice in meaningful impact assessment. This means, for example, that the effectiveness of a programme is measured firstly by distributing a standardised questionnaire to the target groups and, secondly, by conducting interviews with staff or holding a group discussion with experts. The specific form the collected data takes (minutes of interviews, minutes of conversations with experts, percentages from a survey, frequency of observation, etc.) depends on the collection methods chosen. The data must therefore be analysed using appropriate analytical methods.