Methodology: The research methods used for a study.
Respondent: A participant in a research process.
Sample: The number of people actually participating in a study.
Random sample: A sample of respondents chosen from the population at random. Also known as probability sample.
Quota Sample: A sample of participants who fall into designated demographic categories (i.e. age) or have specific traits necessary for the study (i.e. buy a particular product). Not a random sample because the participants are targeted for specific reasons.
Stratified random sample: A quota sample for which each sub-sample is selected at random.
Convenience sample: A sample selection method based on who can be reached quickly, efficiently, inexpensively or easily. No attempt to verify a representative cross-section of the target audiences. Subject to significant bias.
Qualitative: Data that cannot be precisely reported as representative of a larger audience. Often used more for exploration or concept validation. Examples include focus groups, small sample studies, and informal or in-depth discussions.
Quantitative: Data that can be scientifically analyzed and given empirical value. Suggests precision of responses, projectable to larger populations. Examples include scientific (random sample) surveys among various audiences.
Bias: Possibility that any aspect of a study misrepresents the true situation. Possible types of bias include question bias, interviewer bias, interviewer errors, environmental (external) bias and various forms of sample bias: non-response, list errors, sub-group absence or dominance.
Confidence interval: The range around a survey result for which there is a specific statistical probability that it contains the true margin of error. Most commonly in practical studies: 95%.