The questionnaire total runs from 0 to 51 with no gap anywhere along it. There is no place in the distribution where “well” becomes “unwell”; the line is drawn, not found.

the line, and what it flags
cutoff used by the file	14
teenagers at or above it	787 of 4,810
share flagged	16.4%
questionnaire range	0 – 51
median total	5
mean total	7.27

the cutoff was verified, not assumed

The source ships a binary depressed column without stating what produced it. So the pipeline tries every cutoff in range and reports how well each reproduces that column across all 4,810 rows. Exactly one is perfect, and the build asserts it — if a future version of the dataset moved the line, the pipeline would fail rather than quietly publish a wrong claim.

cutoff	agreement with the file's own column
bdi_total ≥ 11	93.16%
bdi_total ≥ 12	95.72%
bdi_total ≥ 13	97.98%
bdi_total ≥ 14	100.00%
bdi_total ≥ 15	97.78%
bdi_total ≥ 16	96.49%
bdi_total ≥ 17	94.80%
bdi_total ≥ 18	93.45%
bdi_total ≥ 19	92.77%
bdi_total ≥ 20	91.83%
bdi_total ≥ 21	90.52%

bdi_total ≥ 14 reproduces the column exactly. The next best, 13, gets 97.98% — close, and wrong.