One matter of the major concerns in college and university courses that require getting data from human subjects involves respect. If your data requires that your subjects do not know of the main goal of your research, does that count as manipulation – a failure to respect their integrity? One way to address this is to ask their consent in advance to be subject to a test or experiment that they will not be fully informed about. “I agree to take test X / answer your questions / drink this liquid / walk down this street, knowing that some social science data is being gathered even though I have not been informed about this data”, or something like that. Sometimes there might be an appeal t future (or retrospective) consent: data might be collected and only later the subject is asked permission to use it. In cases when getting future consent is impracticable or impossible, there may be a case for hypothetical consent: the person would consent if she was fully informed, etc.
Consenting to be subject to medical trials may be problem-free, though in some cases there can be significant difficulties. Imagine an institute wants to try out its new cure-for-cancer treatment drug and asks you to participate with the knowledge that you may be given a placebo. You may wish to be part of the trial but only if you have a chance to be given the new drug that is being tested. Another troubling matter concerns the same test but with children. When might a parent be true to her or his role as a mother or father if the parent consents for their child to be subject to a test without knowing whether the child would be given the new experimental drug or the placebo.