Module 6-Slides Flashcards
Measurement
Process of assigning NUMERALS to variables to represent QUANITITIES of characteristics according to certain rules
Construct
An ABSTRACT variable that is not observable and is defined by the measurement used to assess it
Considered a latent trait because it reflects a property within a person and is not externally observable
~intelligence, health, pain, mobility, and depression
Purpose of Measurement
Way of understanding, EVALUTING, and differentiating characteristics of people, objects, and systems by scientists and clinicians
Allows to communicate in ONJECTIVE TERMS, giving a common sense of “how much” or “how little” w/out ambiguous interpretation
Levels of Measurement
Nominal
Ordinal
Interval
Ratio
Ratio
Distance, age, time, decibels, weight / Numbers represent units with equal intervals, measured from true zero
*The highest level of measurement with an absolute zero point
Interval
Calendar years, Celsius, Fahrenheit / Numbers have equal intervals, but no true zero
*Possesses rank order but also has known and equal intervals between consecutive values but no true zero
Ordinal
Manual muscle test, function, pain assessment scale / Numbers indicate rank order
*A rank-ordered measure where intervals between values are unknown and likely unequal
Nominal
Gender, blood type, diagnosis, ethnicity / Numerals are category labels
*Classifies objects or people into categories with no quantitative order
T/F Measurements cannot be taken at different LEVELS or rated using various SCALES.
False; Measurements CAN be taken at different LEVELS or rated using various SCALES
Example: pain measurement
yes or no: nominal scale
from 0-10: ordinal scale
Why is it important to accurately identify the “level” of measurement?
Because Selection of Statistical tests is based on certain assumptions about data including but not limited to the level of measurement
Parametric tests
Arithmetic manipulations requiring Interval or Ratio level of data
Nonparametric tests
Do not make the same assumptions; are used with Ordinal or Nominal data
Reliability
The extent to which “a measured value can be obtained CONSISTENTLY during REPEATED assessment of unchanging behavior”
What are the 2 basic types of measurement error?
Systematic error
Random error
Systematic error
Predictable, occurring in a consistent overestimate or underestimate of a measure
Random error
Have no systematic bias and can occur in any direction or amount