Glossary S-Z

Glossary S-Z

Sample is a sub-group of the population of interest that has been selected for study.

Sample Size is the number of sample units to be included in the sample.

Sampling Error is the error in a survey caused by using a sample to estimate the value of a parameter in the population.

Sampling Frame is a list of the population of interest that is used to draw the sample in a survey, eg a telephone directory or a list of members of a profession.

Sampling Frame Error is a type of non-sampling error in a survey caused by a sampling frame containing either more or less of a particular type of potential respondent, compared with the population of interest.

Scales (aka Rating Scales) are measurement devices that allow respondents to report the degree of their opinions. Scales are usually in the form of statements or numbers. Pictures may also be used – see pictorial scale.

Screening is the procedure of asking specific questions to determine whether respondents are eligible to participate in a particular research study. This is done at the very beginning of an interview.

Screening Questions are the questions at the beginning of an interview or questionnaire to ensure that a potential respondent is eligible for the survey.

Secondary Data are data that have already been collected and published for another research project (other than the one at hand). There are two types of secondary data: internal and external secondary data.

Segmentation is the process of dividing markets into groups of consumers who are similar to each other, but different to the consumers in other groups.

Selection Bias is a type of non-sampling error where the sample units are selected for treatment in a particular way that produces a different profile to the population. Selection bias can be introduced by researchers and/or by respondents (putting themselves into groups to which they aspire to belong, but they do not currently belong).

Self-selection Bias is a type of non-sampling error that occurs when respondents who chose to participate in some research are systematically different to the intended sample. This type of bias is caused by some types of respondent replying to a survey invitation more than others.

Significance Test is an analysis of sample data to determine whether the data supports a hypothesis about the population from which it was drawn.

Simple Random Sample (aka Random Sample) is a type of probability sample where all units in a population of interest have an equal, known and non-zero chance of being selected.

Skewness refers to the symmetry of a distribution. A skewed distribution is one where the mean, the median and the mode have different values, whereas in a symmetrical distribution they all have the same value.

Skip Pattern (aka Branching Question) is a question used to guide an interviewer through a survey to different questions (ie skipping some questions), depending on the answers given.

Surveys involve a (statistically) large number of interviews with respondents, using pre-designed questionnaires.

Target Population see population of interest.

Telephone Interview is where participants are asked survey questions over the telephone. Telephone interviewing is usually conducted from a central telephone interviewing facility.

Terminate is when an interview is stopped before completion. This may occur for one of three reasons: (1) The respondent gives a non-qualifying response and the interviewer is instructed to TERMINATE AND TALLY. (2) The interviewer decides to stop the interview because of a language problem or disability on the part of the respondent. (3) The respondent refuses to complete the entire survey.

Termination Rate is the number of eligible respondents who do not complete an interview once started.

Topline Report is a brief summary of the main findings of a study.

Universe see population of interest

Validity is the extent to which a research process is accurate and reflects actual market conditions (ie it is free from systematic error).

Verbatim (aka Verbatim Statement) is a reproduction of all of a respondent’s opinion of an object or concept word-for-word, without any omissions, abbreviations or interpretations by the interviewer.

Weighted Sample is a sample to which weighting has been applied.

Weighting is when the responses from some (or all) sub-groups are assigned a statistical weight to reflect the importance of the sub-group in the population of interest.