W11: Measurement and Sampling Flashcards
What is measurement?
fundamental part of scientific research; assignment of values (numbers) to objects, events, outcomes
process of observing, recording observations that are collected
requires rules, isomorphism, indicators of control, operational definition/procedure for measuring
Give an example of measurement for each type: objects, events, outcomes.
objects: hospitals (per geograph. radius)
events: deaths
outcomes: quality of life
What are the different levels/scales of measurement?
-nominal
-ordinal
-interval
-ratio
Define nominal level
numbers are used as labels where they have an inherent numerical value eg. gender, ethnicity
Define ordinal level
numbers are a rank order and are assigned a rank value
define interval level
10-20, 30-40, etc.
knowing rank order and exact distance between each observation
define ratio level
type of number that has true zero
Why is the level important?
helps you decide how to interpret data from variable
helps you decide what stat analysis is appropriate on values that were assigned
What is reliability?
occurs when measurement tool measures same thing more than once and results in same outcomes
aka consistent
What are the types of reliability?
test- retest reliability
parallel forms reliability
inter-rater reliability
Define test-retest reliability. What is the method?
measures how stable a test is over time (keep conditions similar for both testing times)
method: do same test at 2 different times to same group of participants
correlate scores at time 1 with scores at time 2
What is parallel forms reliability? What is the method?
measure of how equivalent 2 different forms of a test is
method: administer 2 different forms of same test to same group of participants
- correlate 2 sets of scores
what is inter-rater reliability? What is the method?
measure of consistency (agreement) from rater to rater
method: have more than 1 rater rate the same thing and correlate the scored between them
How can you increase reliability?
-eliminate items in a test that are unclear, ambiguous, faulty, vague
-standardize conditions under which test is taken
-minimize effects of external events so that true test performance is not affected
- maintain consistent scoring procedures
-standardize instructions to respondents
What is validity?
occurs when test/instrument measures what it is intended to measure; refers to results of a test
aka truthfulness
What is external validity?
research results apply to people and situations beyond particular sample studied
What is internal validity?
degree to which an experiment is designed so that a causal relationship can be demonstrated
What are the different types of validity?
-face
-content
-criterion
-construct
What is face validity?
declaration by researchers claiming instrument is reasonable successful in measuring what it is intended to measure
- based on expert opinion
give an example of face validity.
questionnaire that is supposed to assess seniors’ nutritional status, you may recruit a few experts in seniors nutrition to review it and judge whether they think items are meaningful
- items about accessibility to food>seniors’ income levels (not direct enough)
What is content validity?
measure of how well items in measurement tool represent entire universe of relevant items
based on expert opinion and theoretical perspectives
Give an example of content validity
measuring QOL in seniors, need comprehensive range of Qs- ensure at least one Q is about appetite because seniors view appetite as key part of QOL.
What is criterion validity?
measure of extent to which test is related to some criterion
-requires prospective study design; aka predictive validity
Give an example of criterion validity
breast self examination (“test”) for predicting a breast cancer diagnosis at some later time
What is construct validity?
measure of how well measurement tool items are tapping into underlying theory, construct, or model of behavior
- tested over time and conditions to see f it hold true in all instances
Give an example of construct validity
does an intelligence test actually measure intelligence?
-no gold standard
- test can discriminate
