I have a bad back and have had it for several years. My doctor asked me if I wanted to take part in a study that looked at exercise to help improve the back. I backed out because every time I went for an exam, I had to spend a long time filling out forms, questionnaires and answering questions that were constantly repeated. After all, how many times can I say that my back hurts and it hurts all the time? What is the purpose of all these questions?
Taking part in a study has many benefits but it can also take up a more time than some people are willing to give. When people are first brought into a study, every step should be explained clearly, from physical examinations to filling out questionnaires to participating in the actual treatments. The issue seems to be that perhaps you didn't understand the explanations or that perhaps you didn't learn about the reasons behind all the different aspects of the study.
At first, many questions need to be answered about who you are (age, employment status, etc) so that the study subjects can be broken down with the statistics. This is very important because this type of information can tell researchers that a person of a certain age with a college education may have one problem, while a person of the same age but with a high school education doesn't.
Some questions are repeated throughout the studies and this is to measure any improvement or changes in your status. So, if you're asked to rate your pain on a scale of zero to 10 before the study begins and then every time you see the doctor, they're looking for changes in your scale. The same thing occurs with questions about movement, function, if you are getting out of the house, and so on. At the end of these studies, this is all tabulated and results are determined - hopefully to help other researchers and, ultimately, the patients.