Types of Enrollment Predictions

ACT develops two types of predictions: enrollment probabilities and indexes.

Enrollment probabilities for ACT score senders, EOS names selected, and inquiry pools are campus specific. That is, they provide the probability that a given student will enroll at a specific institution.

The indexes provide a probability that a student will show a specific enrollment behavior.

  • The Mobility Index indicates the likelihood that a student will enroll at an out-of-state institution.
  • The Institution Type Index predicts the likelihood that a student will enroll at a private institution.
  • The Selectivity Index predicts the selectivity of the institution at which the student is likely to enroll.
Campus-Specific Predictions Student-Specific Predictions
Based Primarily on Student Choice Set
  • Probability of enrollment (e.g., 0.43)
  • Probability percentile rank (e.g., 66)
  • Mobility Index (e.g., 0.23)
  • Mobility Index percentile rank (e.g., 45)
  • Institution Type Index (e.g., 0.23)
  • Institution Type Index percentile rank (e.g., 45)
  • Selectivity Index (e.g., 2.6)
  • Selectivity Index percentile rank (e.g., 45)

Predicting Out-of-State Enrollment

The Mobility Index predicts the likelihood that a student will enroll at an out-of-state institution, using (1) the student choice set or campus mix (campuses to which students send scores), (2) ACT Composite score, (3) preferred distance from home to campus, and (4) selected other variables.

The pie chart below shows the relative importance of specific factors in the Mobility Index model.

The campus mix comprises 84% or more than 4/5 of the Mobility Index model. This large percentage indicates that student enrollment behavior is very intentional and predictable. If students send scores to out-of-state institutions, they are much more likely to enroll out of state. If students do not send scores to out-of-state institutions, they are very unlikely to enroll out of state.

Predicting Enrollment at a Private Institution

The Institution Type Index predicts the likelihood that a student will enroll at a private institution, using (1) the student choice set or campus mix (campuses to which students send scores), (2) ACT Composite score, (3) preferred institution type, and (4) selected other variables.

The pie chart below shows the relative importance of specific factors in the Institution Type Index model.

The campus mix comprises 65% or 2/3 of the Institution Type Index model. Preferred institution type accounts for another quarter of the model. Together, the campus mix and preferred institution type account for almost 90% of the model.

This large percentage indicates that student enrollment behavior is very intentional and predictable.

Predicting Enrollment by Selectivity of Institution

ACT classifies colleges and universities into five selectivity categories: highly selective, selective, traditional, liberal, and open.

The Selectivity Index is a number from 5 to 1 (with one decimal place) that predicts the selectivity of the institution at which the student is likely to enroll, using (1) the student choice set or campus mix (campuses to which students send scores), (2) ACT Composite score, (3) high school GPA, and (4) selected other variables. ACT inserts the Selectivity Index into score-sender and EOS records, along with institution-specific enrollment probabilities.

The pie chart below shows the relative importance of specific factors in the Selectivity Index model.

The campus mix comprises 79% or more than 3/4 of the Selectivity Index model. ACT Composite score accounts for another 14% of the model. Together, the campus mix and ACT Composite score account for 93% of the model.

This large percentage indicates that student enrollment behavior is very intentional and predictable. Students are very likely to send scores to institutions that are similar in selectivity to the institution at which they will eventually enroll.