Answer:
The correct option is (a).
Explanation:
The dependent t-test (also known as the paired t-test or matched-samples t-test) compares the two means associated groups to conclude if there is a statistically significant difference amid these two means.
We use the paired t-test if we have two measurements on the same item, person or thing. We should also use this test if we have two items that are being measured with a unique condition.
For instance, an experimenter tests the effect of a medicine on a group of patients before and after giving the doses.
In this case the researcher selected a random sample of the sleep quality of lonely people and the random sample of the sleep quality of non-lonely people.
Both the sample in this case are selected from two very different population.
This clearly indicates that the study design is for non-related samples.
Thus, the correct option is (a).