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Random Error - Error in measurement due to the transient aspects of the person or measurement situation.
Randomized Block Design - Experiment design in which units are arranged into homogeneous groups in order to eliminate differences between groups and increase experimental accuracy.

Randomized Response Model - Interviewing technique in which potentially embarrassing and relatively innocuous questions are paired, and the question the respondent answers is randomly determined.

Range - The distance between the largest score and the smallest score in a distribution.

Rating Scales - Questions that ask respondents to assign specific values to a characteristic in order to establish a common basis for comparison. There are four types of rating scales, each allowing a certain level of analysis on the data collected: nominal, ordinal, interval, and ratio.

Ratio Scales - At the highest level of measurement, they have the attributes of magnitude, equal intervals, and absolute zero. Measurements can range from nonexistent to existent, but never negative. Examples are height, age, weight, and income.

Refusals - Nonsampling error that arises because some designated respondents refuse to participate in the study.

Relative Frequency - A proportion of the frequency of an interval in relation to the total number of frequencies of the distribution.

Reliability - Similarity of results provided by independent but comparable measures of the same object, trait, or construct.

Research Design - Framework or plan for a study that guides the collection and analysis of the data.

Research Process - Sequence of steps in the design and implementation of a research study, including problem formulation, determination of sources of information and research design, determination of data collection method and design of data collection forms, design of the sample and collection of the data, analysis and interpretation of the data, and the research report.

Response Rate - Measure used to evaluate and compare interviewers in terms of their ability to induce contacted respondents to participate in the study.