After week 3 of the second semester, you should submit a single-page document showing your initial results. This should include a sketch of any apparatus you are using for your main experiment. If your project is about data analysis of external data, show a flow diagram representing the analysis protocol instead. If you're writing code, similarly, a flow diagram would be appropriate. Add to this a typical data set that you have actually measured or analysed, and a sentence or two explaining how you will be dealing with such data. Joint students on ph356 don't submit this as assessed work, but it's a worthwhile exercise anyway.
The purpose of this exercise is to make sure you've got a working set-up and can obtain usable data before you start the core part of your experimental programme. Use your preliminary results sheet to discuss your experiment with your supervisor. At this point, the data acquisition and analysis protocol should be finalised - if there are any changes necessary at this stage, they need to be implemented quickly!