This design begins at the start of the project; however, baseline data is collected on for the project group and not for a comparative group. The reasons for not including a comparative group could be lack of awareness of evaluation design, budget, time, or other constraints.
This design works best IF (yes, a big if) the project is based on and adheres to already reasonably proven theory of change, strategies, and interventions related to the outcomes being measured in a similar context. This design is more useful to understand how the process of project implementation accomplished expected outcomes.
The basic flaws of this design are that it cannot provide very precise estimates of project's impact on the outcomes and that due to lack of a comparative group it is difficult to determine the potential for scaling-up the project.
Again, to improve on this design, other methods need to be used such as key informant interviews, focus group discussions, in-depth interviews, and personal history recall.