There might be rare scenarios where no similar participants and comparison students can be matched, i.e. no matches are found during prediction-based propensity score matching (PPSM). This scenario is most likely to occur for an individual term included in analysis with little data. If no participants and eligible comparison students could be matched for a term, the lift in persistence cannot be calculated and the 'Impact by Term' chart will not include a bar for that term.
Some common reasons why no matches could be found include:
- Very small number of submitted participants and/or eligible comparison students were available for matching
- Very small number of submitted participants and/or eligible comparison students from the same term or student group were available for matching
- There is a significant difference between the submitted participants and eligible comparison students, particularly in terms of persistence likelihood and/or propensity to participate in the initiative, for example:
- Participants were all new students, but eligible comparison students were all continuing students
- Participants were all online students, but eligible comparison students were all on-ground students
- Participants were all undergraduates, but eligible comparison students were all graduate students
To avoid this issue, verify that the submitted initiative data accurately represents the impact analysis question you are trying to answer. In particular, confirm that the participants and eligible comparison group were defined correctly in your student list file.