Meta-analysis is a statistical technique used to combine the results of multiple studies, while the other options are methods for evaluating the effectiveness of individual programs.

The primary goal of an impact assessment is to determine the extent to which a program has achieved its intended objectives and outcomes.

Cost-benefit analysis is a quantitative method that compares the costs and benefits of a program to determine its overall effectiveness.

Evaluating the effectiveness of social welfare programs is challenging due to a combination of factors, including lack of data, political interference, and ethical considerations.

Key informant interviews are a qualitative method that involves conducting in-depth interviews with individuals who have knowledge or expertise about a particular program or issue.

The main difference between a randomized controlled trial and a quasi-experiment is that randomized controlled trials use a control group, while quasi-experiments do not.

Conditional cash transfer programs, microfinance programs, and public works programs have all been shown to be effective in reducing poverty.

The primary goal of a process evaluation is to assess how a program is being implemented and managed, and to identify any areas where improvements can be made.

All of the options are examples of outcome indicators that can be used to evaluate the effectiveness of a social welfare program.

Conducting an impact assessment of a social welfare program is challenging due to a combination of factors, including lack of data, political interference, and ethical considerations.

Early childhood education programs, school feeding programs, and conditional cash transfer programs have all been shown to be effective in improving educational outcomes.

The primary goal of a cost-benefit analysis is to determine whether the benefits of a program outweigh its costs.

Immunization programs, maternal and child health programs, and HIV/AIDS prevention and treatment programs have all been shown to be effective in improving health outcomes.

The main challenge in conducting a meta-analysis of social welfare programs is the heterogeneity of studies, which can make it difficult to compare the results of different studies.

After-school programs, job training programs, and community policing programs have all been shown to be effective in reducing crime.