Subjects and Benefits of researches

1

• Subjects and Benefits of researches
• Formulation of hypothesis
• Prof. Dr. Meltem ÇÖL
• Ankara University Medical Faculty Department of
  Public Health

2
Subject of study

• In a study plan first step is
• Decide subject
• Determine aim of study

3
Sources of subjects

• Observations of researcher
• Persons experiences
• Advice's of people who is working in this topic
• Literatures
• Researchers interests
• Researchers knowledge

4
Study subject

• When we decide a study subject we must pay
  attention to these factors
• Study subject
• should be important for public health
• may be common, causes high morbidity and/or
  mortality
• or
• unknown subjects, interesting subjects,
  original subjects, so searching this subject must
  be usefull for science and practice.

5
Study subject

• Do not repeat known subjects which are done by
  previous authors and everything is known about
  it.
• Dont say I can search same subject once more.
• When you choose a subject, you must clarify your
  aim.

6
Study subject

• The research mustn't include too many subject.
• Subject must be specific limited
• So it can be searched deeply

7
Stages for solving health problems

• Descriptive studies
• Analytic studies
• Experimental studies
• Application and carry-out for people
• Healthy people

8
Hypotheses

• Hand washing is the most important factor for
  prevention of infections
• Good health habits (exercise, balanced diet..)
  protect from some diseases.
• Rubella can cause congenital defects
• AIDS can not be transmitted by saliva
• Elevated blood pressure is a risk factor for CHD.

9
RESEARCH TYPES

• Observational Studies
• Descriptive studies (Correlational studies, Case
  reports, Case series, Cross-sectional surveys)
  Can formulate hypothesis
• Analytic studies (Case-control studies, Cohort
  studies) Can test hypothesis
• Experimental (intervention) studies (Randomized
  controlled trial, Field trial, Community trial)
  Can test / prove hypothesis

10
Hypothesis formulationfrom descriptive studies

• There are three methods of hypothesis formulation
  about etiology of disease
• 1) Method of difference
• 2) Method of agreement
• 3) Method of concomitant variation

11
Hypothesis formulation 1) Method of difference

• If the frequency of disease is different, in two
  places or two groups, the disease may be caused
  by some particular factor that differs between
  them.

12
1) Method of difference
Example 1
JAPAN Stomach cancer ? Ovary, Uterus and prostat
cancer ?
USA Stomach cancer ? Uterus, colon and prostat
cancer ?
Hypothesis Some environmental or life style
factors are effective on cancers, if we change
them we can prevent some cancers
13
1) Method of difference
Example 2
Married women have a child Cervix cancer ?
Unmarried women Cervix cancer ?
Hypothesis Marriage ( to have sexual partner)
and to give birth are effective factors on cervix
cancer.
14
Hypothesis formulation2) Method of agreement
A single factor is common in different
circumstances in which a disease occurs with high
frequency Example
Hemophiliacs AIDS ?
IV drug abusers AIDS ?
Recipients of transfusion AIDS ?
Hypothesis One transmission way is bloodstream
for AIDS virus
15
Hypothesis formulation3) Method of concomitant
variation

• Frequency of a factor varies in proportion to the
  frequency of disease

FACTOR ?
DISEASE ?
Hypothesis This factor is effective for this
disease
16
3) Method of concomitant variation
Example Corelational studies are useful for this
type of hypothesis formulation
Colon cancer
Meat consumption
Hypothesis Meat causes colon cancer
17
Hypothesis formulationfrom descriptive studies

• Hypothesis formulation begins with description of
  disease
• Description of disease person, place, time
• Person (age, sex, religion, marital status, etc.)
• Place (Where the rates of disease is highest and
  lowest-region, country, rural / urban, etc.)
• Time When does the disease occur (seasonal,
  years, etc.)

18
Hypothesis formulationfrom descriptive
studiesPerson

• Example Coronary disease death rates by age and
  sex
• Age Men Women
• 15-34 6.4 3.2
• 35-44 60.6 16.2
• 45-54 265.6 71.2
• 55-64 708.7 293.7
• 65-74 1669.9 769.4
• 75 5751.5 4359.0
• Hypothesis Estrogen has protective effect,
  early menopause increases the risk of coronary
  disease

19
Hypothesis formulationfrom descriptive
studiesPlace

• Example England has a high rate of lung cancer
  and a low rate of liver cancer. Japan has a high
  rate of stomach cancer and low rates of
  prostate, ovary and uterus cancer
• Hypothesis Cancer is avoidable.
• Stomach cancer risk
• Japanese in Japan 8.4
• Japanese in USA 3.8

20
Hypothesis formulationfrom descriptive
studiesTime

• Example In Germany (1959) a single case report
  Extremely unusual congenital malformation
  affecting limbs-digits.
• The cases increased 200 fold between 1957-1961 .
• Thalidomide (a sleeping pill) first introduced in
  Germany in 1956.
• In November 1961 hypothesis formulated
  Thalidomide was responsible of the malformations