'A central question we will address is: how do evaluation approaches under cost and time constraints affect the validity of the evaluation design and the conclusions derived from the analysis? What are acceptable compromises that permit valid findings and what are the minimum methodological requirements without which a study can no longer be considered a quality impact evaluation? Section 2 considers a range of options for simplifying the design of an evaluation, and examines the implications for evaluation rigor and cost. Section 3 presents options for selecting comparison groups, while Section 4 looks at the use of secondary data. Strategies for reconstructing baseline data, to improve an evaluation's rigor, are examined in Section 5, while options to reduce the costs of data collection are outlined in Section 6. Finally, the ways in which budget, time and data constraints reduce the rigor of an evaluation are reviewed in Section 7. This section also presents a range of options for addressing each of these constraints.'