The Vignette is a method for collecting data by presenting hypothetical situations, and asking research participants a set of directed questions to reveal their values and perceptions.
This methodology is often used when dealing with sensitive and difficult topics like substance abuse or sexuality. It allows the interviewee to distance himself from the situation so that he will be free to answer candidly without fear of being judged negatively.
For example, in predicting whether participants in an alcohol treatment program were likely to drop out, they were given a set of vignettes which depicted normal social drinking behaviors, and problem drinking behaviors. Their ability to distinguish between normal and problematic drinking behavior was used as a predictor of whether they were likely to be successfully rehabilitated or not. (O'Connor, Davies, Heffernan, & van Eijk, 2003)
This method may also be used when you want to ask research participants to voice their opinion on topics which they may not have had personal experience.