10-8b Principles of Measurement

Question 1

What do tests and measures encompass?

Answer 1

body structure & function, activities, participation, outcome measures

Question 2

What do tests and measures’ properties rely on?

Answer 2

Psychometric properties of tools:

reliability, SEM, MDC, MCID, validity, etc.

Question 3

What are some questions you should be asking yourself about a measurement?

Answer 3

Do I understand what I am measuring?
How confident should I be about the result?
What can I infer from this measurement?
How well does this measurement represent my patient’s capacity/ability/impairment/status/etc?

Question 4

What are the different levels of measurement?

Answer 4

Nominal
ordinal
interval
ratio

Question 5

What is a nominal scale? Examples?

Answer 5

names
Categories without order 
(Frequency, tallies, counts, percentage, mode)
Falls risk vs. non-falls risk
Practice setting
insurance

Question 6

What is an ordinal scale? examples?

Answer 6

order but no consistent intervals (can have mode, median, and range)
MMT as “poor, fair, normal”
Categories with order
Involves central tendency: mode, median range
Mid mod max assistance model
Box and whiskers
BMI classifications

Question 7

What is an Interval scale? Examples?

Answer 7

order and equal intervals
The time between values is meaningful
Can be negative

Question 8

What is a ratio scale? example?

Answer 8

has order, intervals, and true 0
TUG
HR
VO2 max
Goniometry
6MWT

Question 9

What do Interval and Ratio scales involve?

Answer 9

Central tendency: mean
Variability: SD
Only forms of data we can find an MDC on

Question 10

What can you report from nominal data?

Answer 10

in each group
% in each group
mode (soccer)

Question 11

What can you report from ordinal data?

Answer 11

in each category
% in each category
Mode
Median
Inter quartile range (IQ) (upper quartile - lower quartile)
Box represents middle 50% and whiskers measure upper and lower 25% in a box and whiskers plot

Question 12

What is precision?

Answer 12

how close/small/precise a measurement can be

Question 13

What is the measurement value equal to?

Answer 13

true value + error

Question 14

What are the types of error?

Answer 14

patient, examiner, environment, instrument

Question 15

What is SEM? What is it based on?

Answer 15

an estimate of the average variability expected around a measurement

Variability in patient performance

Variability in measurement process

Question 16

what is CI in regards to SEM?

Answer 16

95% CI = X +/- ~2 SEM

Question 17

95% CiM?

Answer 17

Measurement +/- 1.96 SEM

68% confidence = 1 SEM

Question 18

Calculating MDC?

Answer 18

First, use SEM to det. CI around a measurement
95% CiM
MDC95 = CiM95 * sqr root of 2 
= (1.96 * sqr root of 2) * SEM
= 2.77 SEM

Question 19

What do you need to calculate SEM?

Answer 19

variability of measures for a tested group (s)
reliability coefficient for tested group (r)

SEM = s * square root of 1 - r

Question 20

How do you calculate intervention effect error?

Answer 20

SEMean

StdError = SD/square root of n

Question 21

How do you calculate Measurement error?

Answer 21

SEMeasurement

SEM = s * square root of 1-r

Question 22

What is reliability?

Answer 22

value that quantifies consistency of a tool

not sufficient for a measure to be valid

Question 23

What is ICC?

Answer 23

Intraclass Correlation Coefficient
(variability b/w subjects - variability within subjects)/variability between subjects

measures reliability of a tool

you want to be as close as possible to 1

Question 24

Inter-rater

Answer 24

between different raters

Question 25

intra-rater or test-restest

Answer 25

within a single rater

Question 26

what is reliability/consistency quantified by?

Answer 26

ICC = 1 = perfectly reliable
ICC = 0.5 = no better than chance

Question 27

What is validity?

Answer 27

whether it measures what it says it measures

criterion, construct validity est. by comparing the measure to something else