Your thesis is a large analytical paper whose purpose is to not only prove that you are familiar with your particular department and subject matter but that you can conduct thorough research on your own that contributes to the field.
Writing an analysis essay means you have to make an argument. The central component to this argument is called your thesis. The thesis is the claim that you make in a single sentence. Your purpose is to make a persistent case that is not readily obvious to the average reader. You should interpret something from the text or about your topic that is then supported by sufficient evidence.
The thesis statement provides your argument, the purpose of your paper summarized into a single sentence. You can choose to place the thesis sentence at the beginning of your introduction or the end of the introductory paragraph. You are not confined to any particular location. Remember that your thesis should be arguable and it should be reasonable. You should not write about something obvious; there is no argument there. Argument means you need analysis. Analysis is when you take things apart and you explain them. If you are unsure of whether your thesis/argument is sound, you can ask yourself to explain the opposite side of your argument. A good thesis will have an opposite side. If there is no opposite side, no other argument to your statement, then you have not selected a topic that is adequate enough for a paper.
You should be able to argue something such as “although X is true about ___ Y is in fact truer”. This type of statement presents both arguments and shows what side of the argument you are on. Your purpose is then to convince the reader that your side is the best. Another way to write your thesis is to use the following form “If we look closely at X we discover that Y”.