1. General Introduction Some Notes

2. Definition of Measurement “Measurement consists of rules for assigning numbers to observable attributes so as to represent quantities of the attributes” 1. “Attributes” can mean dimensions, properties, characteristics, or behaviors (e.g., height, density, cost, physical function) 2. If it’s not observable, it’s not measurable (but let’s define observable very broadly). 3. “Operational definitions” indicate how to measure an attribute that is not directly observable (e.g., health, quality of care)

3. Classification of Health Measures 1.Measures may be classified by their purpose: –Evaluative (e.g., outcome measures) –Diagnostic (e.g., BP, ESR) –Prognostic (e.g., Apgar; screening tests) –Discriminative (e.g., IQ tests) –Measures for Individuals or Groups

4. Classification (2) 2. Measures may be classified descriptively: –Scope of the measure (e.g., specific or generic) –Qualitative vs. quantitative 3. Or methodologically: –Subjective vs. objective –How administered (questionnaires, rating scales) –Structured vs. semi-structured –How they are scored: indexes vs. profiles

5. Scale Types Discrete or continuous variables Nominal (e.g., sex; blood type). You can count these Ordinal (house numbers; “mild pain”). apply Interval (  C; Jan. 9, 2005). You can add, subtract Ratio (weight; BP; # doctor visits). You can multiply & divide these (Mnemonic: NOIR)

6. What’s an Index? Standard, weighted composite set of indicators Gives a broad-spectrum indication of general level of the attribute Generally used for broad comparisons Examples: consumer price index; hospital activity index; Health Utilities Index

7. Choosing & Using Scales Choosing Criteria for evaluating a test Off the peg, or design your own? Where do you get information on it? What type: Specific or generic? Objective or subjective? Using Measures: Practical issues Interview or self- administered? How to scoring it? Analyzing scores Interpreting them

8. Old Ways of Administering Health Questionnaires Are Not Practical Face-to-face Interview$200 + Telephone Interview $ 50 + Self-administered$ 20 + Computerized via Web$ <5?

9. Cone of Measurement Demands: How much effort does it require of the respondent? IQ tests, etc. HRQOL. ADLs. EKGs

10. The Ideal Measurement and the Dilemma of Short Forms Short Forms (same number of items) 1 1 2 2 3 Measure too low (ceiling effect) Broad spectrum, but too few marks (low discrimination) The Ideal (Source: John Ware, October 2000)

11. Match the Instrument to the Application 1 2 3 4 1 2 3 4 1 2 3 4 Population Monitoring Outcomes Research Patient Management Source: John Ware, October 2000