All corrections
1
Claim
In 1840, over a third of the British population worked in a factory.
Correction

This overstates factory employment. Historical sources say roughly a third of the workforce was in manufacturing in 1841, not a third of the total population in factories.

Full reasoning

The "over a third" figure comes from historical census summaries of manufacturing employment, not from counts of the entire population working in factories.

Two separate problems make the sentence inaccurate:

  1. Population vs. workforce: The Office for National Statistics' historical census summary says manufacturing accounted for 36% of the workforce in 1841. That is not the same as 36% of the total population.
  2. Manufacturing vs. factories: The Vision of Britain historical database warns that 19th-century manufacturing figures overstate factory work, because many people classified as in manufacturing actually worked in small workshops behind shops, not in factories.

So the sentence inflates the claim twice: it turns a statistic about the workforce into one about the whole population, and it turns manufacturing into factory work. A more accurate version would be that in 1841, about a third of the workforce was in manufacturing.

2 sources
Model: OPENAI_GPT_5 Prompt: v1.16.0