But let me briefly disagree with this statement:
Rogers Smith, a political scientist at the University of Pennsylvania who has been active in the “Perestroika” movement, said that the question should determine the method. If you want to test cause and effect, “quantitative methods are the preferred way to go,” he said, but they can’t tell “how political phenomena should be understood and interpreted” — whether a protest, for instance, is the result of a genuine social movement or an interest group, whether it is religious or secular.
Actually, quantitative methods are pretty terrible at testing causality. They are great at examining relationships, but they can't tell us what is causing what. For example, quantitative methods might help us see that there is a firm relationship between ice cream sales and drowning deaths, but it requires either interviews, reading, or human intuition to figure out that neither is causing the other, and that temperature is causing both. This is why I favor a mixed-methods approach, although it can be challenging to get that published sometimes.