In some cases, rather than following a group of people from a specific point in time onwards, the researchers take a retrospective approach, working backwards as it were. They might ask participants to tell them about their past behaviour, diet or lifestyle (. their alcohol consumption, how much exercise they did, whether they smoked etc.) They might also ask for permission to consult the participants’ medical records (a chart review). This is not always a reliable method and may be problematic as some people may forget, exaggerate or idealise their behaviour. For this reason, a prospective study is generally preferred if feasible although a retrospective pilot study preceding a prospective study may be helpful in focusing the study question and clarifying the hypothesis and feasibility of the latter (Hess, 2004).
Hybrid methods use a creative form of product usage to meet their goals. For example, participatory-design methods allows users to interact with and rearrange design elements that could be part of a product experience, in order discuss how their proposed solutions would better meet their needs and why they made certain choices. Concept-testing methods employ a rough approximation of a product or service that gets at the heart of what it would provide (and not at the details of the experience) in order to understand if users would want or need such a product or service.
In most cases a random sampling is used, which is where each member of the population has an equal chance of being selected. There are several techniques for choosing a population sample, and they must be as unbiased as possible. One technique involves assigning each member of a population a number, starting at 0, and using a random number generator to pick numbers (and thus members) from the population. Another method primarily used if the population is very large is to sort the population by a key (name, ID number) and then pick every nth member.