Quantitative methods - including performance testing, indoor air pollution monitoring and questionnaires - can track changes in "quantifiables" and are a means of objectively comparing one intervention against another. Qualitative methods, on the other hand, help reveal the perspectives of individuals or communities and provide important contextual data to explain the results of quantitative analyses. They include in-depth, open-ended interviews, direct observations of behaviours and participatory methods. Sample size, . the number of individuals, homes or stoves to monitor, is a critical aspect in evaluation planning. If the sample size is too large, time and financial resources are wasted on superfluous data collection. If the sample size is too small, it is impossible.
