lecture 1 introduction to course introduction to measurement

Lecture 1

• Introduction to course

• Introduction to measurement

Pre-requisite (or co-requisite)

• 606

• 607

• or permission of instructor

Format

• Lectures

• Guest lectures

• Small group discussions/presentations– group and room assignments to be posted on

web-page

• Information on web-page– Detailed schedule on web-page– Course objectives on web-page

Web-page

• Detailed schedule

• Course objectives

• Lectures

• Small group exercises – guidelines– group assignments

• Assignments

• Other?

Readings

• Course packs:– 1) required readings– 2 additional readings– more to come!

• Available at Copies Nova – (corner of Sherbrook and Peel)

Assessment

• Assignments (20%)– 4, graded by TA

• Paper critiques (10%)– 5

• To be posted on web-page with due date

• Work handed in late will not be accepted!

Assessment (cont)

• Mid-term exam (30%)– Monday Nov 10, 11:00 - 12:30

• Final exam (40%)– Monday Dec 15, 9:00 - 12:00

Introduction to measurement

• Purposes of measurement

• Types and sources of data

• Types of variables

• Questionnaires

• Types of scale

Purposes of measurement

• Clinical– screening, diagnosis, monitoring in individuals

• Surveillance – planning and monitoring public health and

health care in populations

• Research– measurement of determinants, outcomes,

confounders/modifiers

Examples of requirements by purpose of measurement

• Clinical– discrimination between health and disease

relevant to management

• Surveillance – valid measurement of trends

• Research– maximize validity of study results

Sources of data

• Primary vs secondary

• Clinical observations

• Questionnaires and interviews

• Reportable diseases and registries

• Health records

• Administrative databases (hospital discharges, claims, medication prescription)

• Vital statistics

Examples of measures: for discussion

• Use of health services during past year (doctor visits, hospitalization)

• Use of alcohol and drugs (current and lifetime)

• Blood pressure (current and during past 5 years)

• Mood/depression (current and lifetime)

Types of variables (level of measurement)

• Continuous (syn. dimensional, quantitative, interval)

• Categorical (discrete)– dichotomous, binary– polychotomous

• nominal

• ordinal

What level of measurement?

• Country of birth

• Blood pressure

• Diagnosis of SARS

• Level of pain

Planning questionnaires

• Open-ended or close-ended

• Level of measurement

• Choice of response scale

Open-ended question

10. What do you like the MOST about St. Mary’s?

___________________________________________

___________________________________________

Question wording:Open- vs close-ended questions

• Close-ended questions– used most frequently– easier to analyze

• Open-ended questions– useful in exploratory research– basis for developing more structured questions in

later research– analysis more time-consuming, requires qualitative

methods

Alternative formatsD.O.B. _____/_____/________

d m yyyy

Age: __________

Age-group:

1 less than 652 65 – 743 75 –844 85 or older

Nominal scale

What is your current marital status?

1 Single (never married)2 Married (including common-law)3 Separated4 Divorced5 Widowed

Ordinal scales

1. Mobility

0 I have (s/he has) no problems in walking about

1 I have (s/he has) some problems in walking about

2 I am (s/he is) confined to bed

Disadvantages of categorical scales

• Loss of information

• Loss of precision

Continuous response scales in questionnaires

• Visual analogue scale

• Adjectival scale

• Likert scale

• Semantic differential scale

Visual analogue scale

Now, to help people say how good or bad theirhealth state is, let’s say the best state you canimagine is 100 and the worst state you can imagineis 0.

In your opinion, how good or bad is your/his/herown health today - please mark on the line below.

0 ___________________________________ 100

Likert scalePlease circle the answer that corresponds best toyour opinion.

1. You are treated with respect

Totally Agree No opinion Disagree Totallyagree disagree

1 2 3 4 5