<p>The sort of things that are on-topic are the statistical aspects of data-collection <em>methods</em>: sampling schemes, surveys, experimental design, &amp;c. So if you want to investigate whether patients with some disease have higher blood pressure than normal, CV would be the right place to ask about choosing an appropriate sample size; but not about how to use a sphygmomanometer, or where to find data on the range of normal blood pressure.</p>
