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.
All of the New England colonies had been covered by ice during the last Ice Age, which created poor, rocky soil. The final melt-back of the glaciers left some of the rocky areas peppered with large boulders.
Rivers are fairly short and their floodplains are narrow, unlike in other areas of America, and do not allow for the creation of huge agricultural plots along their banks.
The major resources available and used by the colonists were lumber and fish.
