Terminology

• Positive Relationship

  A relationship in which the two variables or measurements tend to change together in the same direction.
• Negative Relationship

  A relationship in which the two variables or measurements tend to change together in opposite directions.
• Validity

  The degree to which the measurement process measures the variable it claims to measure.
• Face Validity


  An unscientific form of validity that concerns whether a measure superficially appears to measure what it claims to measure.
• Concurrent Validity


  The type of validity demonstrated when scores obtained from a new measure are directly related to scores obtained from a more established measure of the same variable.
• Predictive Validity

  Demonstrated when scores obtained from a measure accurately predict behaviour according to a theory.
• Construct Validity

  Requires that the scores obtained from a measurement procedure behave exactly the same as the variable itself. Construct validity is based on many research studies that se the same measurement procedure and grows gradually as each new study contributes more evidence.
• Convergent Validity

  Is demonstrated by a strong relationship between the scores obtained from two (or more) different methods of measuring the same construct.
• Divergent Validity

  Demonstrated by showing little or no relationship between the measurements of two different constructs.
• Reliability

  A measurement procedure is the stability or consistency of the measurement. If the same individuals are measured under the same conditions, a reliable measurement procedure produces identical measurements.
• Observer Error

  The individual who makes the measurements can introduce human error into the measurement process, especially when the measurement involves a degree of human judgement.
• Environmental Changes

  Although the goal is to measurement the same individual under identical circumstances, this is difficult to attain. Often, there are small changes in the environment from one measurement to another, and these small changes can influence the measurements.
• Participant Changes

  The participant can change between measurements. Small changes within the participant, like attention span, hunger, sleepiness, etc. can cause the obtained measurements to differ, producing what may appear to be inconsistent or unreliable measurements.
• Test-Retest Reliability

  Established by comparing the scores obtained from two successive measurements of the same individuals and calculating a correlation between the two sets of scores.
• Inter-rater Reliability

  The degree of agreement between two observers who simultaneously record measurements of the behaviours.
• Split-Half Reliability

     Obtained by splitting the items on a questionnaire or test in half, computing a separate score for each half, and then calculating the degree of consistency between the two scores for a group of participants.
• Scale of Measurement

  The set of categories used for classification of individuals. The four types of measurement scales are nominal, ordinal, interval, and ratio.
• Nominal Scale

  A scale of measurement in which the categories represent qualitative differences in the variable being measured. The categories have different names but are not related to each other in any systematic way.
• Ordinal Scale

  A scale of measurement on which the categories have different names and are organised sequentially.
• Interval Ratio

  A scale of measurement in which the categories are organised sequentially, and all categories are the same size. The zero point of an interval scale is arbitrary and does not indicate a total absence of the variable being measured.
• Ratio Scales

  A scale of measurement in which the categories are sequentially organised, all categories are the same size, and the zero point is absolute or nonarbitrary and indicates a complete absence of the variable being measurement.