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This material indicated about measurement of scale, data collection tools and tools development
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Scales of measurement and Data collection MeduicineStudents Diriba D. (MPH-Epidemiology) Tel: 0917793542 August 3, 2022
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.
Types of scales of measurement • Nominal scale: uses names, labels, or symbols toassign each measurement to one of a limitednumber 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
Cont… There are three things to remember: • Anything that can be measured falls into one of the four levels; • The higher the type, the more precision in measurement; and • Every level up contains all the properties of the previous level.
Variables Variable: A characteristic which takes different values in different persons, places, or things. E.g. Age, sex, SBP, Height…. • Qualitative variable: The notion of magnitude is absent • Quantitative variable: Variable that has numerical magnitude. • Discrete variable: It can only have a finite number of values in any given interval. • Continuous variable: It can have an infinite number of possible values in any given interval.
Data Collection Data • The raw material of statistics is data. • For example: • the number of patients attends some clinics (counting). • When a nurse weighs a patient (measurement)
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.
Data Collection… Sources of Data • 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.
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: • Observation checklist • Face-to-face interviews questionnaire • Self-administered interviews questionnaire • Postal or mail method and telephone interviews • Using available information/secondary data • Focus group discussions (FGD) giudeline • Key informant interview (KII) checklist
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.
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
3. Use of documentary sources Examples include: • Official publications of Central Statistical Authority • Publication of Ministry of Health and Other Ministries • News Papers and Journals. • Records of hospitals or any Health Institutions.
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
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.
Types of Questionnaire • 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.
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.
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?''
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.
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.
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
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
