THE RESULT
What the data shows
The largest computed metric is 0.25 for 81 / origin 2; the smallest is 0 for 70 / origin 2. Metric: missing_share (Missing share).
The question-mark marker has been converted to NaN. Zero missingness in a subgroup does not prove representative sampling.
| model year | origin | vehicles | missing | missing share | group |
|---|---|---|---|---|---|
| 81 | 2 | 4 | 1 | 0.25 | 81 / origin 2 |
| 80 | 1 | 7 | 1 | 0.1429 | 80 / origin 1 |
| 80 | 2 | 9 | 1 | 0.1111 | 80 / origin 2 |
| 74 | 1 | 15 | 1 | 0.06667 | 74 / origin 1 |
| 71 | 1 | 20 | 1 | 0.05 | 71 / origin 1 |
| 82 | 1 | 20 | 1 | 0.05 | 82 / origin 1 |
| 70 | 2 | 5 | 0 | 0 | 70 / origin 2 |
| 72 | 1 | 18 | 0 | 0 | 72 / origin 1 |
| 71 | 3 | 4 | 0 | 0 | 71 / origin 3 |
| 71 | 2 | 4 | 0 | 0 | 71 / origin 2 |
| 70 | 3 | 2 | 0 | 0 | 70 / origin 3 |
| 70 | 1 | 22 | 0 | 0 | 70 / origin 1 |
THE METHOD
From source to answer
Explicit missing indicators summarized over recorded groups.
The Python source exposes this study’s transformations. The complete project download includes shared preparation and evaluation routines.
THE NEXT DECISION
What follows from the finding
Review source availability before interpreting imputed horsepower or dropping vehicles.
Where the conclusion stops
Historical city-cycle vehicle observations are not current fleet performance. Vehicle mix and model year are confounded. A '?' horsepower value means missing, not zero.
Related studies may reuse observations or holdouts. These are historical analyses; associations and backtests do not demonstrate commercial impact. Further model tuning needs new, untouched evaluation data.