Please help me with my question about psychological research..?

Sometimes different types of research methods are important because you get different types of results. Example: Testing a product under different types of lights, (red, blue, green, white) give either the same answer or different answers. In psychology this is important to determine that the answer is whether it is biased or unbiased based on the different tests. That therefore determines the result which is based on the tests and the results and not a bias. This is where ethical problems would arise if there was only one research method. They would question the method. They would question the process and they would question the outcome. You can not do research based on one question. Therefore having more than one research method can actually specifically narrow the rate of outcome and not of a flippant guess. FYI: I'm sure whatever you wrote is fine because as it states those ethical problems can really get in the way of your research.