Final answer:
The study conducted during National Public Health week, where students were asked about their caffeine consumption habits and headaches, is an observational study.
Step-by-step explanation:
The type of study that was conducted during National Public Health week, where students were asked about their caffeine consumption habits and headaches, is an observational study.
This study involves gathering information from a group of people without manipulating any variables. The researchers did not intervene or control any factors, but instead observed and recorded data.
In this case, the researchers were interested in understanding the relationship between caffeine consumption and headaches among the student population.