Answer:
Observational study
Step-by-step explanation:
The study shown in the question above is an example of an observational study. In this type of study, the researcher separates two groups of people, where the variables will be tested. These groups are contrasting with each other, which promotes the comparison on how the variables behaved in each group.
In the study shown in the question above, the researcher should separate the groups between right-handed and left-handed people and make assessments of how it affects their health, decreasing the life expectancy of each one.