In this post “missing data” does not mean absence of whole categories of data, which is a common enough problem, but missing data values within a given data set. While this is a common problem in almost all spheres of research/evaluation it seems particularly common in more qualitative and participatory inquiry, where the same questions may not be asked of all participants/respondents. It is also likely to be a problem when data is extracted from documentary source produced by different parties e.g. project completion reports.