The interviewer would like to know what you consider your greatest strength as a clinical researcher. This helps them to understand where you would best fit, should you be given the opportunity.
Yes, you can brag about yourself! It's tough to do sometimes, so you may want to create and memorize a definite answer before your interview. Be sure to reinforce that others have endorsed your best skills.
"In the past, I have received regular positive feedback on my ability to manage multiple projects while keeping consistent and accurate data. If I had to choose my strongest skill as a clinical researcher, I would choose my ability to multitask."
"As my career in clinical research is new, I would say my strongest skill is my blend of education and willingness to learn. I am a sponge for information at this point in my career and truly want to learn. I am excellent with accepting, and implementing, feedback."
"I excel in a few areas, but I would say my greatest strength in clinical research has been my ability to coordinate and analyze various data sets. When data is coming from multiple channels, it can be challenging to bring it all together to support a single hypothesis. I have been successful in working with complex data sets."