A comparison of two methods for classifying trajectories: a case study on neighborhood poverty at the intra-metropolitan level in Montreal
Bibliographic record
Abstract
In recent years several studies have examined changes in the distribution of poverty in the North American cities, with most empirical work assessing neighborhood change between two time points. This paper aims to make a methodological contribution to the study of neighborhood change, by comparing two classification methods, one classical (k-means clustering) the other more novel (Latent Class Growth Modelling; LCGM) to identify groups of census tracts having followed similar trajectories of poverty in the Montreal metropolitan area, Canada. Here trajectories of poverty are measured over a twenty-year period, using five time points. The relative performance of the LCGM vs. the k-means clustering was assessed using a series of multinomial logistic regressions examining how different socioeconomic variables were associated with the trajectories of poverty. Results showed that k-means and LCGM identified similar groups of census tracts characterized by ascending, descending, or stable poverty levels throughout the period, with LGCM only marginally outperforming k-means clustering.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.015 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.003 | 0.005 |
| Science and technology studies | 0.004 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".