1.An investigator wants to assess whether the use of a specific medication given to infants born prematurely is associated with developmental delay. I

Step 1
The cohort study generally involves a group of individuals that meet a set of criteria at the study start, who are disease free. The cohort is followed for few years and the associations are estimated between risk factor and the outcomes.
In the above study, the cohort is ‘the infants born prematurely’, who are followed for 2-years. They are divided into two groups to study that the specific medication given to them is associated with development delay. So, the risk factor is the ‘specific medication’ and the outcome is the ‘development delay’.
Thus, the type of the study design is ‘the cohort study’.
As the study involves some participants in the start and followed going forward in time, it is a ‘prospective study’.
Step 2
In the above study the confounding is more of an issue, as it may lead to distortion of the association between the premature born infants and the development delay.
The confounding is the misrepresentation of the effect of the risk factor on an outcome by another characteristic.
Some of the factors that may contribute to this problem are:
Socio-economic background of the family, maintenance of hygiene, some serious health issues in mother, environmental factor and so on.