The sample size was too large. Scientists did not run the study. Women were excluded from the study. No medication was given to the men.
A research study concluded that people who work longer hours increase their chances of having higher blood pressure. This conclusion was developed from a study of 200 men of different ages. How is this investigation biased?

Options:
- The sample size was too large.
- Scientists did not run the study.
- Women were excluded from the study.
- No medication was given to the men.

Women were excluded from the study.