Levels Of Measurement

Concepts of Measurement

Measurement Theory Concepts Directness of Measurement  Direct measurement • Oxygen saturation, Temperature, weight  Indirect

measurement

• Pain, depression, coping, selfcare, self-esteem

Multiple Measures of Abstract Concept Rating Scale Likert Scale

Pain

Observation

Physiologic Measures

Measurement Theory Concepts  Measurement Error 

Systematic error – an error that is not

random but occurs consistently such as a weighing scale that inaccurately weighs subjects 3 pounds heavier than they are 

Random error – an error that cause

individuals’ observed scores to vary haphazardly around their true scores.

Levels of Measurement Nominal Ordinal Interval Ratio

Gender 1 = Male 2 = Female

Likert Scale  How often do you feel in control of

your life?  (1) Never  (2) Seldom  (3) Often  (4) Almost always

Age How old are you? _______ years What LOM? ___________

Age  How old are you?  25-34  35-44  45-54  55 or older 

What LOM? __________

Income  1 = under $35,000  2 = $35-50,000  3 = $50 - 100,000  LOM? _________

Reference of Measurement Norm-Referenced Testing: Test performance standards that have been carefully developed over years with large, representative samples using a standardized test with extensive reliability and validity.

Reference of Measurement  Criterion-Referenced Testing: Comparison of a subject’s score with a criterion of achievement that includes the definition of target behaviors. When behaviors are mastered, the subject is considered proficient in the behaviors.

What is reliability?  Reliability is concerned with

how consistently the measurement technique measures the concept of interest.

Types of Reliability Stability -- is concerned with the consistency of repeated measures or test-retest reliability

Types of Reliability  Equivalence--is focused on comparing two versions of the same instrument (alternate forms reliability) or two observers (interrater reliability) measuring the same event.

Types of Reliability  Homogeneity--addresses the correlation of various items within the instrument or internal consistency; determined by split-half reliability or Cronbach’s alpha coefficient.

Inter-rater reliability  Consistency in raters  % = # behaviors

performed/ total # of behaviors

What is validity? The extent to which an

instrument reflects the concept being examined.