The main way to make sure you are keeping to the question is by referring it to the source. Linking your own knowledge of statistics, studies and theory will show great application skills. Directly quoting the source at the start of each paragraph will show that you are linking it specifically to what they are asking for. The relevance of your application is also vital, showing that you are not just trying to mould it to what you already know but drawing links which are rational and show you have a diverse range of knowledge.