問題文
A regional health authority must publish hospital waiting times by condition and district. Small cells would reveal individuals. Three techniques are on the table: suppress cells below a threshold, widen the district into a region, and add small random noise to each figure. Which statement describes what each of the three does to the published table?
選択肢
- Suppression removes the small cells, generalization merges them into larger ones, and perturbation keeps every cell but makes each figure approximate.
- Suppressing merges the small cells into larger ones so that no cell falls below the threshold, generalization keeps every cell but replaces each figure with an approximation derived from the surrounding cells, and perturbation removes the cells that cannot be protected any other way, which makes perturbation the most aggressive of the three.
- None of the three helps, because the totals can be used to recover the suppressed cells, so the only safe option is to stop publishing the table by district.
- All three produce the same table, because each of them prevents a small cell from being read, so the authority can pick whichever is easiest to implement in its reporting tool.