AQA GCSE Statistics

## The five stages of the cycle Statistics is the practice of answering a question with data, and the **statistical enquiry cycle** is the order in which that work is done. It runs through five stages: the work is planned first, the data is collected, it is processed and presented, the results are interpreted, and the whole enquiry is then evaluated and reviewed. The last stage feeds back into the first, because what is learned from one enquiry usually sharpens the question for the next, which is why it is drawn as a cycle and not as a line. Every technique in the course sits inside one of these stages. Choosing a sampling method belongs to planning and collection, drawing a histogram or finding a standard deviation belongs to processing, and saying what a correlation coefficient means belongs to interpretation. A piece of statistical work is judged on how well the stages fit together as much as on any single calculation. ## Questions and hypotheses An enquiry begins with a question or a hypothesis. A **hypothesis** is a statement that can be checked against data, for example "pupils in Year 11 spend more time on homework than pupils in Year 8" or "the price of a used car falls as its age increases". A question such as "how do pupils spend their evenings?" is also a valid start, but it does not say what result would count as an answer, so it is usually turned into one or more hypotheses. A hypothesis can only be tested by collecting and analysing suitable data. Opinion…