This document discusses data collection techniques and statistics. It defines statistics and differentiates between descriptive and inferential statistics. It describes various sources of data, including primary and secondary sources. Techniques for collecting primary data are discussed, including observation, questionnaires, and interviews. It defines variables and different types of variables. Methods for revising and correcting data to avoid errors are also presented.

1. Data Collection
Maha Basodan, MBBS, MSc, MPH
Department of Community Medicine and Public Health

2. Learning outcomes
By the end of this lecture, students will be able to;
Differentiate between different sources of information
Describe procedures for collection of information
Differentiate between different techniques for data collection
Discuss the concept of Biostatistics, statistical method, descriptive and
inferential statistics.
Describe types of variables

3. • When you hear that heart disease is number one cause of
death in the world….. How did we know this?
• When you hear that smoking and diet rich in Cholesterol
are risk factors for heart disease… how did we know this?

4. Have you wondered how do we do such table?

5. Have you ever wondered how do we do such graph?

6. What is statistics?
• Statistics with a capital S is the name of science that has a great
importance and usage by other sciences.
• Statistics is the science concerned with scientific methods for collecting,
organizing, summarizing, presenting and analyzing data as well as drawing valid
conclusions and making reasonable decisions on the basis of such analysis.

7. Statistics has two parts:
Statistics
Inferential
Descriptive

8. Descriptive and Inferential Statistics
• Descriptive Statistics allows for collection, processing, summarizing and
presentation of data ONLY. No conclusion or inference about a larger group.
• Inferential Statistics allows to use values that are drawn from a sample to make
decisions about the population from which the sample was taken.

9. Stages of statistical method
1- Planning
2-Data collection
3- Data processing
4- Data analysis and
interpretation
a. Statement of problem
b. Definition of objectives
c. Review and evaluation
d. Hypothesis formulation
e. Planning of the work
a. Data organization
b. Data summary
c. Data presentation

10. 1- Data collection

11. SOURCES OF INFORMATION
According to origin of information
- PRIMARY
A datum is collected DIRECTLY from the element that originates it.
- SECONDARY
A datum is collected from an INTERMEDIATE source, not directly
from that element that originates it.

12. PROCEDURES FOR DATA COLLECTION
1- CENSUS:
Procedure for the collection of information about ALL
the elements of interest in a country or a given
territory in a SPECIFIC PERIOD.

13. TYPES OF CENSUS:
1-FACTUAL
Each element of the population is enumerated in the PLACE WHERE
THEY ARE at the census hour.
2-DE JURE
Each element of the population is enumerated according to THEIR
HABITUAL PLACE of living.

14. CENSUS REQUIREMENTS:
-INDIVIDUALITY
-UNIVERSALITY
-SIMULTANEITY
-PERIODICITY
-TERRITORIALITY

15. 2-SURVEY:
Procedure that OCCASIONALLY and with a SPECIFIC
OBJECTIVE is used for the collection of information about
population’s sample or a given sector of the population.

16. Survey characteristics
No periodicity
No systematization
Partial purpose
Done when needed
Specific objective

17. 3-REGISTER:
Procedure for a CONTINUOUS and SYSTEMATIC
collection of SPECIFIC information.
Example: death register, birth register

18. TECHNIQUES FOR DATA COLLECTION
from primary source
1- OBSERVATION
2- QUESTIONNAIRE
3- INTERVIEW

19. 1- OBSERVATION
Perceptive process through which the attention is focused on the
element that is being studied.
FACTORS INFLUENCING OBSERVATION:-
 Object or subject observed
 Observer
 Means of observation
 Environmental conditions
 System of knowledge

20. ADVANTAGES
Most objective.
Direct contact observer – observed Feasible of repetition.
Not difficult.
Commonly used in medicine.
DISADVANTAGES
Not for great amount of persons.
Highly qualified personnel.
Not for subjective information.
Might be expensive.

21. 2- QUESTIONNAIRE
Any PRINTED format aimed toward the data collection that at the
same time facilitates the data compilation.
FACTORS INFLUENCING QUESTIONNAIRE:-
 Topics in a logical order.
 Without ambiguities.
 Allow easy compilation.
 Accurate responses.
 Space for answer.
 Design according to data processing.

22. TYPES OF QUESTIONNAIRE:
OPEN, CLOSED and OPEN - CLOSED
ADVANTAGES :-
 For great amount of persons.
Not Highly qualified personnel.
For subjective information.
 Is cheap.
DISADVANTAGES :-
Memory dependent responses.
 Answers depend of the respondent’s interpretation.
Different results according to type of questions

23. 3- INTERVIEW
Active process of obtaining information by means of an ORAL
INTERROGATION and an observation of the interviewed by the
interviewer.
CONSIDERATIONS:
 A guide for interview.
 The personality of the interviewed.
 Not influence the answer.
 The cultural level of the interviewed.
 The environmental conditions.

24. ADVANTAGES:
-Interrogation- observation
-Direct contact
-Subjective aspects
-Clarify answers
DISADVANTAGES :
Not for great amount of persons.
Highly qualified personnel.
Very expensive.
Memory and good intentions.

25. But, what do we collect in these techniques?
We collect…….! Data ? Variables ?

26. 26
A variable : is any characteristic, related to:
subjects, objects or events, can be measured , and is liable
to variation or change (assumes different values for
different elements or within elements at different
occasions). For example: age, sex, weight, marital status
and blood group are variables

27. ACCORDING TO THE TYPE OF VARIABLE
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Continuous Discrete
Age, Weight
Blood sugar
No. of cases
No. of rooms
Nominal Ordinal
Marital status,
Sex,
Nationality
Education level
Degree of burn
Quantitative (Numerical) Qualitative (or categorical)

28. Quantitative Continuous
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Obtained by measurements
Can have any value between 2
values (fraction)
Quantitative Discrete
Obtained by counting or enumeration
Only integer number
Qualitative Nominal Groups the elements according to the
characteristics (cannot be ordered)
Qualitative Ordinal Ordered Arrangement
ACCORDING TO THE TYPE OF VARIABLE

29. REVISION AND CORRECTION OF DATA
CAUSES OF ERRORS:
During the captation process.
During the compilation process.
Accidental errors.
Systematic errors (Bias)

30. MEASURES TO AVOID ERRORS DURING DATA CAPTATION
ACCIDENTAL ERRORS
Non common result, repeating.
To exclude an ambiguous answer.
To revise all data of each element

31. SYSTEMATIC ERRORS:
Periodical revision of the procedures.
Periodical revision of the means.
Periodical revision of environmental conditions.
To establish uniform criteria.

32. DURING DATA COMPILATION (BOTH)
To revise the data while it is being compiled.
The observer should compile the data by himself.
Each datum in its specific place.
To avoid rewriting

33. ‫كملـــــــــــــــــنا‬
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