Main Points

What Are Data?

• The term "data" refers to the kinds of information researchers obtain on the subjects of their research.

Instrumentation

• The term "instrumentation" refers to the entire process of collecting data in a research investigation.

Validity and Reliability

• An important consideration in the choice of an instrument to be used in a research investigation is validity: the extent to which results from it permit researchers to draw warranted conclusions about the characteristics of the individuals studied.
• A reliable instrument is one that gives consistent results.

Objectivity and Usability

• Whenever possible, researchers try to eliminate subjectivity from the judgments they make about the achievement, performance, or characteristics of subjects.
• An important consideration for any researcher in choosing or designing an instrument is how easy the instrument will actually be to use.

Ways to Classify Instruments

• Research instruments can be classified in many ways. Some of the more common are in terms of who provides the data, the method of data collection, who collects the data, and what kind of response they require from the subjects.
• Research data are data obtained by directly or indirectly assessing the subjects of a study.
• Self-report data are data provided by the subjects of a study themselves.
• Informant data are data provided by other people about the subjects of a study.

Types of Instruments

• Many types of researcher-completed instruments exist. Some of the m ore commonly used are rating scales, interview schedules, tally sheets, flowcharts, performance checklists, anecdotal records, and time-and-motion logs.
• There are also many types of instruments that are completed by the subjects of a study rather than the researcher. Some of the more commonly used of this type are questionnaires; self-checklists; attitude scales; personality inventories; achievement, aptitude, and performance tests; projective devices; and sociometric devices.
• The types of items or questions used in subject-completed instruments can take many forms, but they all can be classified as either selection or supply items. Examples of selection items include true-false items, multiple-choice items, matching items, and interpretive exercises. Examples of supply items include short-answer items and essay questions.
• An excellent source for locating already available tests is the ERIC Clearinghouse on Assessment and Evaluation.
• Unobtrusive measures require no intrusion into the normal course of affairs.

Types of Scores

• A raw score is the initial score obtained when using an instrument; a derived score is a raw score that has been translated into a more useful score on some type of standardized basis to aid in interpretation.
• Age/grade equivalents are scores that indicate the typical age or grade associated with an individual raw score.
• A percentile rank is the percentage of a specific group scoring at or below a given raw score.
• A standard score is a mathematically derived score having comparable meaning on different instruments.

Measurement Scales

• Four types of measurement scales -- nominal, ordinal, interval, and ratio -- are used in educational research.
• A nominal scale involves the use of numbers to indicate membership in one or more categories.
• An ordinal scale involves the use of numbers to rank or order scores from high to low.
• An interval scale involves the use of numbers to represent equal intervals in different segments on a continuum.
• A ratio scale involves the use of numbers to represent equal distances from a known zero point.

Preparing Data for Analysis

• Collected data must be scored accurately and consistently.
• Once scored, data must be tabulated and coded.