General Introduction Some Notes Definition of Measurement Measurement

Definition of Measurement “Measurement consists of rules for assigning numbers to observable attributes so

Classification of Health Measures 1. Measures may be classified by their purpose: – Evaluative

Classification (2) 2. Measures may be classified descriptively: – Scope of the measure (e.

Scale Types Discrete or continuous variables • Nominal (e. g. , sex; blood type).

What’s an Index? • Standard, weighted composite set of indicators • Gives a broad-spectrum

Choosing & Using Scales Choosing • Criteria for evaluating a test • Off the

Old Ways of Administering Health Questionnaires Are Not Practical • • Face-to-face Interview Telephone

Cone of Measurement Demands: How much effort does it require of the respondent? IQ

The Ideal Measurement and the Dilemma of Short Forms Broad spectrum, but too few

Match the Instrument to the Application Population Monitoring Outcomes Research Patient Management 4 4

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General Introduction Some Notes

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)

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

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

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)

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

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 selfadministered? • How to scoring it? • Analyzing scores • Interpreting them

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

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

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

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