# ChatGPT Conversation Sample

## Conversation

Case-Control Study OR

## User

Explain, solve, explain.

The prompt is an outbreak epidemiology exercise. It gives 26 cases and 26 controls from the same hotel population and asks for 2 x 2 tables for foods eaten at lunch.

## ChatGPT

This is a case-control outbreak investigation, so the correct measure of association is the odds ratio, not the risk ratio.

In a case-control study, the crude odds ratio is:

OR = (a d) / (b c)

where:

- a = exposed cases
- b = unexposed cases
- c = exposed controls
- d = unexposed controls

## ChatGPT

The food-specific tables produce these odds ratios:

| Food | Cases ate | Cases did not eat | Controls ate | Controls did not eat | Odds ratio |
| --- | ---: | ---: | ---: | ---: | ---: |
| Pasta with meat sauce | 25 | 1 | 18 | 8 | 11.11 |
| Grilled steak | 23 | 3 | 18 | 8 | 3.41 |
| Russian salad | 10 | 16 | 5 | 21 | 2.63 |
| Tiramisu | 7 | 19 | 3 | 23 | 2.82 |

Pasta with meat sauce has the largest odds ratio.

## User

Sure.

## ChatGPT

Submission-ready answer:

Because this is a case-control study, I constructed a 2 x 2 table for each food and calculated the odds ratio.

Pasta with meat sauce had the highest odds ratio, about 11.11. That means the odds of having eaten pasta with meat sauce were about 11 times higher among cases than among controls.

Therefore, pasta with meat sauce is the food most strongly associated with the outbreak and is the most likely vehicle of infection.