Measurement and Sampling Flashcards
what is measurement
when a researcher measures, he or she takes a concept, idea, or construct and develops a measure (i.e. a technique, a process, a procedure) by which he or she can observe the idea empirically
two types of measurement process
- conceptualisation
- operationalisation
conceptualisation
- refinement of abstract concepts
- process of thinking through the various meanings of the concept
operationalisation
- development of specific research procedures that will result in empirical observations
- important in research as they are measurable and allow for replication
Example of conceptualisation and operationalisation definitions for “criminality”
conceptual: non-sanctioned acts of violence against other members of society or their property
operational: counting number of criminal arrests, or number of times a person has spent in prison, or asking people whether they have committed crimes
levels of measurement
Categorical
- the average it has NO MEANING
- example: average smoker
Continuous
- the average HAS MEANING
- example: average age or blood pressure
Discrete variables
- a variable that can only take on a certain number of values
- categorical variables are considered to be discrete variables
nominal measurement
used to categorise data into mutually exclusive categories or groups
e.g., Faculty (Beedie, FASS), eye colour
- categorical level of measurement
- least precise level of measurement
ordinal measurement
used to measure variables in a natural order, such as rating or ranking
e.g., socioeconomic status
- categorical level of measurement
- mutually exclusive
interval measurement
used to measure variables with equal intervals between values. But these variables have no TRUE zero
e.g., temperature. A temperature of 0 does not mean no temperature
- continuous level of measurement
ratio measurement
allows for comparisons and computations such as ratios, percentages, and averages
e.g., height, weight
- continuous level of measurement
Distinguishing levels of measurement example: John is 10 years old and Sam is 20 years old (which is nominal, ordinal, interval, and ratio?)
Nominal: john is young and Sam is old
Ordinal: John is younger than Sam
Interval: John is 10 years younger than Sam
Ratio: Sam is twice as old as John
what is reliability?
the ability of a measuring instrument to produce consistent results under consistent conditions
Types of reliability
Measurement
- test-retest
- reliability across time
Inter-rater
- independent evaluations conducted by different individuals
Parallel forms reliability
- reliability across indicators
Internal consistency
- whether different items on the same test correlate
How to improve reliability
- conceptualization
- increase level of measurement (use ratio instead of an ordinal variable)
- multiple indicators
What is validity?
the degree of confidence we can place on the inferences we make about people based on their scores from that scale