When are key impact assessment methods appropriate?

Sample Surveys are appropriate when:

The intervention affects large numbers
Accurate estimates of impact are required
Statistical comparisons must be made between groups over time and/or between locations
Delivery/implementation mechanisms are operating well, thereby justifying investment in the assessment of impacts
The target population is heterogeneous and it is difficult to isolate the factors unrelated to the intervention

Rapid Appraisal and/or PLA are appropriate when:

The intervention is promoting participatory principles in (re)-planning, implementation, monitoring and evaluation
An understanding of motivations and perceptions is a priority
One of the purposes of the study is to assess whether or not felt needs are being addressed by the intervention
The impact of community-based organisations or other institution building activities are of importance
There is a need to understand the quality of the data collected through surveys
There is a need for contextual studies before designing more complex monitoring or impact assessment exercises (e.g. case studies or surveys)

Participant Observation and /or Case Studies are appropriate when:

An understanding of motivations and perceptions is a priority
Other methods are unlikely to capture the views of women, minorities and other disadvantaged groups
One of the purposes of the study is to assess whether or not felt needs are being addressed by the intervention
The impact of community-based organisations or other institution building activities are of importance
There is a need to understand the quality of the data collected through surveys or rapid appraisals (e.g. causal processes of poverty)
There is a need for contextual studies before designing more complex monitoring or impact assessment exercises (e.g. before carrying out rapid appraisals or before designing a survey)

Sample Surveys are usually not appropriate when:

An intervention affects a small number of people
Policymakers are mainly concerned about the outcomes of the intervention e.g. how many people use the health clinic?
Implementation is recent and untested and it is likely that the way in which the intervention is implemented will have little impact in the present time
The purpose of the assessment is to study complex activities or processes (e.g. the development and operation of community based organisations in poor communities)
The purpose of the assessment is to document easily observable changes in the physical environment or other tangibles
The purpose of the assessment is to understand whether or not the intervention is meeting the felt needs of the beneficiaries

Rapid Appraisal and/or PLA are not usually appropriate when:

Interventions are relatively un-complex, in which bounded locations are not units of analyses (e.g. health centres serving a wide catchment area)
Indicators of impact are uncontroversial and negative impacts are unlikely
Standardised and statistically representative generalisations for large and diverse populations are regarded as the sole priority
Participation of beneficiaries is not a priority

Participant Observation and/or Case Studies are usually not appropriate when:

The intervention is small and ‘uncomplicated’ providing a specific service or limited intervention which is unlikely to affect community dynamics beyond a few specific effects (e.g. diseases specific health facilities or campaigns)
Bounded locations are not units of analysis
Indicators of impact are clear and easily measurable or assessable ( by survey or rapid appraisals)
Indicators of impact are uncontroversial and negative impacts are unlikely
Information is needed quickly, and standardised, statistical representative generalisations are regarded as the sole priority

Source: Herbert and Shepherd, 2001

Chronic Poverty Research Centre