sampling

Audit Sampling Tools

This directory contains simple audit sampling utilities. The production-ready CLI is audit_sample.py; the older sample.py, sample.html, and stratified_sample.py examples remain for compatibility and learning.

Purpose

audit_sample.py generates reproducible, documented samples from CSV and Excel populations. Each run writes the selected sample, validated population, reconciliation files, methodology notes, a manifest, and a log suitable for an audit workpaper package.

Installation

Sampling needs only the analysis extra (pandas + Excel support):

pip install ".[analysis]"

Supported input formats are .csv, .xlsx, .xls, and .xlsm.

Random Sampling Example

python sampling/audit_sample.py \
  --input sampling/examples/users_population.csv \
  --id-column "User ID" \
  --method random \
  --sample-size 5 \
  --seed 20260707 \
  --out ./output

Stratified Counts Example

python sampling/audit_sample.py \
  --input sampling/examples/changes_population.csv \
  --id-column "Change ID" \
  --method stratified \
  --stratify-column "Change Type" \
  --strata-counts "Normal=3,Emergency=2,Standard=2" \
  --seed 20260707 \
  --out ./output

Stratified Proportions Example

python sampling/audit_sample.py \
  --input sampling/examples/changes_population.csv \
  --id-column "Change ID" \
  --method stratified \
  --stratify-column "Change Type" \
  --strata-proportions "Normal=0.50,Emergency=0.25,Standard=0.25" \
  --sample-size 8 \
  --seed 20260707 \
  --out ./output

Validate-Only Example

python sampling/audit_sample.py \
  --input sampling/examples/changes_population.csv \
  --id-column "Change ID" \
  --method validate-only \
  --filter "Status=Closed" \
  --out ./output

YAML config files are also supported. CLI arguments override config values:

python sampling/audit_sample.py --config sampling/examples/stratified_config.yml

Output Files

Each run creates sample_<YYYY-MM-DD>_<HHMMSS> under the selected output directory.

• sample.csv: selected sample rows for random and stratified runs.
• population_validated.csv: population after filters, blank-ID handling, and dedupe handling.
• population_reconciliation.csv: row-count tie-out metrics.
• excluded_rows.csv: rows removed by filters, blank-ID exclusion, or dedupe.
• duplicate_ids.csv: duplicate ID rows when duplicates are identified.
• strata_summary.csv: requested and actual counts for stratified runs.
• methodology.txt: audit workpaper narrative.
• manifest.json: machine-readable run metadata, input hash, options, and output list.
• run.log: start time, warnings, errors, output folder, and status.

Reproducibility

Provide --seed to make row selection reproducible for the same input and options. If no seed is provided for sampling, the tool generates one, prints a warning, and records the generated seed in manifest.json and methodology.txt.

The tool samples without replacement. Stratified sampling derives each stratum seed from the base seed by adding the stratum index.

Limitations

Filters are exact matches in Column=Value form only. The tool does not yet perform monetary-unit sampling or statistical sample-size calculation.