WEEK THREE: MEASUREMENT, RELIABILITY, VALIDITY

Question 1

Measurement

Answer 1

if a thing exists in some amount; and if exists in some amount, it can be measured

Question 2

Count

Answer 2

the number of occurrence of an event

Question 3

Ratio

Answer 3

• relationship between 2 numbers
• Numerator not necessarily included in the denominator
• Ex. (binary) sex ratio

Question 4

Odd

Answer 4

The probability of an event occurring relative to it not occurring

Question 5

Rate

Answer 5

*Speed of occurrence of an event over time
*Numerator: no of EVENTS observed for a given time
*Denominator: population in which the events occur

Question 6

Prevalence Rate

Answer 6

the proportion of the population (or population sample or sample subset) that has a given disease or other attribute at a specified time
* Obtained from cross sectional studies

Question 7

Formula of Point prevalence rate

Answer 7

= # with disease at specific time/ population at same time

Question 8

Period Prevalence Rate Formula

Answer 8

with disease at specific time period/ total defined population at same period

Question 9

What is the Incidence Rate

Answer 9

the proportion of the population at risk that develops a given disease or other attribute during a specified time period
* Obtained from cohort (longitudinal) studies

Question 10

Formula of Incidence Rate

Answer 10

of new events during a specific time period/population “at risk”

Question 11

What are the 4 hallmarks of Health studies

Answer 11

1) A research question/plausible theory
2) A well thought design to address the research question
3) Measurement of exposure and outcome
4) Analysis to compare groups

Question 12

Relative Risk

Answer 12

• Tells us how many times as likely is that someone who is ‘exposed’ to something will experience a particular health outcome compared to someone who is not exposed
• Tells us about the strength of an association
• Can be calculated using any measure of disease occurrence e
  o Prevalence
  o Incidence rate

Question 13

Random Error vs. Systematic Error

Answer 13

random: due to chance
systematic: due to recognizable source
- can have both

Question 14

Calculation of relative risk

Answer 14

=[a/(a+b)] / [c/c+d)]

Question 15

Non Differential Misclassification

Answer 15

• when the probability of individuals being misclassified is equal across all groups in the study
• Usually weakens associations – brings effect estimates (RR, OR, AR) closer to the null value
• 10%

Question 16

Differential Misclassification

Answer 16

misclassification of exposure is not equal between subjects that have or do not have the health outcome, or when misclassification of the health outcome is not equal between exposed and unexposed subject
- 20%

Question 17

Precision VS. Accuracy In Measurement

Answer 17

A measurement tool/scale with high precision is reliable
A measurement tool/scale with high accuracy is valid

Question 18

Insufficient precision occurs bc

Answer 18

1. The measurement tool is not precise enough
2. (independent) interviewers rate the same person differently using the same scale (inadequate training)
3. The sane interviewer rates the same person differently

Question 19

incidence vs prevalence

Answer 19

Incidence
Measures frequency of disease onset
- What is new
Prevalence
Measures population disease status
- What exists

Question 20

Internal Consistency

Answer 20

• present when the items in a survey measure various aspects of the same concept
  Ex. “i enjoy eating most fruits” and “i do not like to eat fruit”. If the answer to the 1st question is yes, the answer to the second should be no. This is evidence that the responses are reliable.

Question 21

Cronbach’s Alpha

Answer 21

measure of internal consistency used with variable that have ordered responses
Expressed with a 0 or 1

Question 22

Reliability

Answer 22

refers to whether a n assessment instrument gives the same results each time it is used in the same setting with the same type of subjects
Means considerable or dependable results
Part of the assessment of validity

Question 23

Validity

Answer 23

Refers to how accurately a study answers the study question or the strength of the study conclusions
For outcome measures (i.e surveys or tests), validity is the accuracy of measurement

Question 24

How can Researchers Enhance the Validity of their Assessment Instruments

Answer 24

1. Do a literature search and use previously developed outcome measures
2. If the instrument must be modified for use with subjects or setting, modify and describe how
3. Test reliability

Question 25

Interrater Reliability

Answer 25

studies the effect of different raters or observers using the same tool and is estimated by percent agreement, kappa (for binary outcomes) or Kendall Tau

Question 26

Construct Validity

Answer 26

Judgment based on the accumulation of evidence form studies using a specific measuring instrument

Question 27

Content Validity

Answer 27

Addresses how well the items developed to operationalize a construct provide an adequate and representative sample of all the items that measure the construct

Question 28

Item Response Theory

Answer 28

Provide an alternative for understanding measurement + strategies for judging the quality of measuring instrument

Question 29

Face Validity

Answer 29

present when content experts and users agree that a survey instrument will be easy for study participants to understand and correctly complete

Question 30

Kuder- Richardson Formula 20 (KR-20)

Answer 30

measure of internal consistency used with binary variable
Expressed with a 0 or 1
Scores near 1 indicate an assessment tool with minimal random error and high reliability