Question

Why do we use independent samples for assessing different populations?

Answer 1

We use independent samples to asses different populations so that we can find the properties that are distinct for each population and unique that is to find if two populations are significantly different. For example ,if we sample blood pressures of 20 patients before and after a dose of a medicine, then the patients with high blood pressure before will also show high blood pressure after even if the values vary. These become dependent samples and it is difficult to know if the medicine is effective . On the other hand if we pick 20 patients and give them the medicine ,call it group 1 and pick a different 20 patients and give them placebos , call them group 2. Here the samples are independent , they do not influence each other and one can easly determine the effectiveness of the medicine.