Measurement of scale in health research

1. Scales of measurement and Data collection
Pharmacy Students
Diriba D. (MPH-Epidemiology)
Tel: 0917793542
August 3, 2022

2. Scales of measurement
 Clearly not all measurements are the same.
e.g. Measuring an individuals weight is qualitatively different from
measuring their response to some treatment on a three category of
scale, “improved”, “stable”, “not improved”.
 Measuring scales are different according to the degree of precision
involved.
 There are four types of scales of measurement.

3. Types of scales of measurement
1. Nominal scale: uses names, labels, or symbols to
assign each measurement to one of a limited
number of categories that cannot be ordered.
Examples: Blood type, sex, marital status
2. Ordinal scale: assigns each measurement to one of a limited
number of categories that are ranked in terms of a graded order.
Examples: Cancer stages, pain
3. Interval scale: assigns each measurement to one of an unlimited
number of categories that are equally spaced.
It has no true zero point.
Example: Temperature measured on Celsius
4. Ratio scale: measurement begins at a true zero point and the
scale has equal space.
Examples: Height, weight, blood pressure

4. Cont…

5. Cont…
There are three things to remember:
1. Anything that can be measured falls into one of the four
levels;
2. The higher the type, the more precision in measurement;
and
3. Every level up contains all the properties of the previous
level.
5

6. Variables
Variable: A characteristic which takes different values in different
persons, places, or things.
E.g. Age, sex, SBP, Height….
1. Qualitative variable: The notion of magnitude is absent
2. Quantitative variable: Variable that has numerical magnitude.
1. Discrete variable: It can only have a finite number of values in any given
interval.
2. Continuous variable: It can have an infinite number of possible values in
any given interval.

7. Data Collection
Data
• The raw material of statistics is data.
 For example:
 When a hospital administrator counts the number of patients
(counting).
 When a nurse weighs a patient (measurement)

8. Data Collection…
Types of data
1. Primary data: collected from the items or individual
respondents directly for the purpose of certain study.
2. Secondary data: which had been collected by certain people
or agency, and statistically treated and the information
contained in it is used for other purpose.
Systems for collecting data
1. Regular system: Registration of events as they become
available.
2. Ad hoc system: A form of survey to collect information that is
not available on a regular basis.

9. Data Collection…
Sources of Data
1. Routinely kept records: e.g. Hospital medical records
contain immense amounts of data on patients.
2. External sources: The data needed to answer a question may
already exist in the form of published reports, commercially
available data banks, or the research literature,
3. Surveys: e.g. If the administrator of a clinic wishes to obtain
information regarding the mode of transportation used by
patients to visit the clinic,
4. Experiments: e.g. If a nurse wishes to know which of several
strategies is best for maximizing patient compliance, she might
conduct an experiment in which the different strategies of
motivating compliance are tried with different patients.

10. Data Collection Methods
• Data collection techniques allow us to systematically collect
data about our objects of study
 Various data collection techniques can be used such as:
1. Observation checklist
2. Face-to-face interviews questionnaire
3. Self-administered interviews questionnaire
4. Postal or mail method and telephone interviews
5. Using available information/secondary data
6. Focus group discussions (FGD) giudeline
7. Key informant interview (KII) checklist

11. 1. Observation
• Observation is a technique that involves systematically selecting,
watching and recoding behaviors of people or other phenomena
and aspects of the setting in which they occur,
• It includes all methods from simple visual observations to the use
of high level machines and measurements, sophisticated
equipment or facilities.
Advantages: Gives relatively more accurate data on behavior and
activities
Disadvantages:
• Investigators or observer’s own biases, prejudice, desires,
• Needs more resources and skilled human power during the use of
high level machines.

12. 2. Interviews and self-administered
questionnaire
• Interviews and self-administered questionnaires are probably the
most commonly used research data collection techniques.
• Designing good “questioning tools” forms an important and time
phase in the development of most research proposals.
What to consider;
• Are our informants mainly literate or illiterate?
– If illiterate, the use of self-administered questionnaires is not an option.
• How large is the sample that will be interviewed?
– The use of self-administered questionnaires is simpler and cheaper; such
questionnaires can be administered to many persons simultaneously

13. 3. Use of documentary sources
Examples include:
1. Official publications of Central Statistical Authority
2. Publication of Ministry of Health and Other Ministries
3. News Papers and Journals.
4. Records of hospitals or any Health Institutions.

14. Common problems of data collection
 Language barriers
 Lack of adequate time
 Expense
 Inadequately trained and experienced staff during data
collection
 Invasion of privacy/ethical issues
 Bias e.g recall bias
 Cultural norms

15. Choosing a Method of Data Collection
• Decision-makers need information that is relevant, timely,
accurate, cost-effective and usable.
• Others pay attention to accuracy and the strength of the method in
using scientific approaches.

16. Types of Questionnaire
1. Open-ended questions
 Such questions are useful to obtain information on:
 Facts with which the researcher is not very familiar,
 Opinions, attitudes, and suggestions of informants, or
 Sensitive issues.

17. Types of Questions…
2. Closed Questions
• Closed questions offer a list of possible options or answers from
which the respondents must choose.
• When designing closed questions one should try to:
 Offer a list of options that are exhaustive and mutually exclusive
 Keep the number of options as few as possible.

18. Steps in Designing a Questionnaire
Step1: Content
• Take your objectives and variables as your starting point
Step 2: Formulating
• Formulate one or more questions that will provide the information
needed for each variable.
• Check whether each question measures one thing at a time.
• Avoid leading questions.
E.g. ''Do you agree that the district health team should visit each
health center monthly?''

19. Cont…
Step 3: Sequencing of Questions
• The sequence of questions must be logical for the respondent
• At the beginning of the interview, keep questions concerning
“background variables”. e.g., age, religion, education, marital
status, or occupation).
• Pose more sensitive questions as late as possible in the interview
• Use simple everyday language.

20. Cont…
Step 4: Formatting the Questionnaire
When you finalize your questionnaire, be sure that:
 Each questionnaire has a heading and space to insert the number,
data and location of the interview.
 Sufficient space is provided for answers to open-ended questions.

21. Cont…
Step 5: Translation
• If interview will be conducted in one or more local languages,
• After having it translated you should have it retranslated into the
original language.
• You can then compare the two versions for differences

22. Cont…
In writing specific questionnaire items:
- Avoid Loaded Questions
- Avoid Leading Questions
- Avoid Double-Barreled Questions
- Use Appropriate Words
- Write Short Questions
- Write Simple Questions