You need to focus on an area you have access to for testing, experimentation and/or modifications and comparisons. It is recommended you select a product that relates to an area of interest and decide on a criteria you wish to evaluate or explore.
For example:
Use a range of research sources, including design, technology and scientific journals and books. When collecting primary research you must assess the validity of your tests and suggest anything that may impact on the tests. You will need to conduct primary research to gather data on your product tests, it is recommended you gather quantitative data, qualitative data may also be useful but offers less reliability.
Display data collected clearly in tables for analysis. Label tables, any diagrams and photos with figures for easy referrals when you’re writing your essay. Collect the data directly after you’re initial Secondary Research and literature review.
Be careful to stay focused, it is easy to go off on a tangent and begin writing about another aspect or criteria related to your product.