It is not possible to convert a raw score into a percentile without knowing the distribution of scores and key parameters of the distribution. Since none of this information is provided, it is not possible to give a sensible answer.
USC's 2014 25th-75th percentile ACT Math Scores are 28-34, meaning 25% of students scored 28 or lower on the ACT Math Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
A percentile depends on the distribution of the observations, not the total number of observations.
1.5 / 34 = 0.0441176 0.044 as a percentile is 4.4%
MIT's 2014 25th-75th percentile ACT Math Scores are 34-36, meaning 25% of students scored 34 or lower on the ACT Math Score, and 75% of students scored 36 or lower (i.e. 25% of students scored 36 or higher).
Carnegie Mellon's 2014 25th-75th percentile ACT scores are 29-34 on the English section, 29-34 on the Math section, and 29-33 Composite.
Amherst's 2014 25th-75th percentile ACT Composite Scores are 30-34, meaning 25% of students scored 30 or lower on the ACT Composite Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Barnard's 2014 25th-75th percentile ACT English Scores are 29-34, meaning 25% of students scored 29 or lower on the ACT English Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Berkeley's 2014 25th-75th percentile ACT English Scores are 27-34, meaning 25% of students scored 27 or lower on the ACT English Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Berkeley's 2014 25th-75th percentile ACT Math Scores are 27-34, meaning 25% of students scored 27 or lower on the ACT Math Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Colgate's 2014 25th-75th percentile ACT English Scores are 30-34, meaning 25% of students scored 30 or lower on the ACT English Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Kenyon's 2014 25th-75th percentile ACT English Scores are 29-34, meaning 25% of students scored 29 or lower on the ACT English Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Penn's 2014 25th-75th percentile ACT Math Scores are 29-34, meaning 25% of students scored 29 or lower on the ACT Math Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Pomona's 2014 25th-75th percentile ACT Composite Scores are 29-34, meaning 25% of students scored 29 or lower on the ACT Composite Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Pomona's 2014 25th-75th percentile ACT English Scores are 30-34, meaning 25% of students scored 30 or lower on the ACT English Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Pomona's 2014 25th-75th percentile ACT Math Scores are 29-34, meaning 25% of students scored 29 or lower on the ACT Math Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Rice's 2014 25th-75th percentile ACT Composite Scores are 30-34, meaning 25% of students scored 30 or lower on the ACT Composite Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).
Scripps's 2014 25th-75th percentile ACT Math Scores are 29-34, meaning 25% of students scored 29 or lower on the ACT Math Score, and 75% of students scored 34 or lower (i.e. 25% of students scored 34 or higher).