As each new day's sample is added, the oldest sample is dropped from the overall result. They are made up of small sample overnight surveys which cannot employ all the rigorous procedures for sampling and selection that less time-sensitive polls might use. For example, they are less likely to call back respondents who were unavailable on the first call, injecting the potential for bias. The assumption, not accepted by everyone, is that averaging the results will make up for problems due to small sample sizes. Focus Groups Focus groups are not polls at all, but qualitative interviews with a small, carefully selected number of people.
Focus groups are neither a form of group interviewing nor serial interviewing.
They generate information based on the give and take of group discussion rather than the one-way flow of regular survey interviews. The groups are usually homogenous, since combining participants with common interests, affiliations or backgrounds theoretically makes it easier to generate a useful or revealing discussion. A heterogeneous focus group, such as one incorporating hard-core conservatives and liberals alike, might either discourage some people from speaking freely or lead to verbal confrontations that exaggerate differences of opinion. A focus group's sample is neither randomly selected nor representative, so you cannot generalize results or compare them statistically. Focus groups offer the palette with which to paint a deeper portrait of opinion in news stories.