5-varialbes.pptx

VARIABLES
By:
Rana Maaz Mohammed Ahmed
• Honour degree in chemical pathology- University of Khartoum
• Master degree in chemical pathology- University of Khartoum
•Higher diploma in research methodology and biostatics –
University of Medical Sciences and Technology
1

 What is a variable?
 A variables any characteristic that can
take different values.
 It could be a characteristic of a subject
(person), object or phenomena.
2

Variables
Quantitative
(numerical)
Age
(E.g. 12
years old)
Qualitative
(categorical)
Gender
(E.g. male
or female)
3

Quantitative
Continuous
(can contain
fractions)
Weight
(48.5kg,70.3kg)
Discrete
(can not
contain
fractions)
Number of
children
(2, 3, 5)
4

Qualitative:
Nominal:
can identify by
names
e.g. Type of fruits
( orange ,
apple…)
Binary Nominal
(binominal): Can put
only in 2 options
e.g. Gender
(male, female)
Ordinal:
Can put in orders
e.g. Socio-economic
status
(v. good, good, bad)
5

in-class exercise:
 Determine the type of variable in the
following table:
6

Variable
Name
Occupation
Height (cm)
No. of pregnancies
Nationality
Age (years)
Religion
Educational level
Eye color
Home-university distance (kms) 7

Variable Type
Name Qualitative- Nominal
Occupation Qualitative-Nominal
Height (cm) Quantitative-Continuous
No. of pregnancies Quantitative-Discrete
Nationality Qualitative-Nominal
Age (yrs) Quantitative-Continuous
Religion Qualitative-Nominal
Educational level Qualitative-Ordinal
Eye color Qualitative-Nominal
Home-university distance (kms) Quantitative-Continuous 8

 Independent and dependent variables:
 Example:
“Is smoking associated with lung cancer?”
We are trying to determine if smoking is
a factor or risk in the development of an
outcome which is lung cancer.
10

 In the previous example of smoking
and lung cancer:
 The independent variable would be
smoking.
 The dependent variable would be lung
cancer.
11

 in-class exercise:
 Article title: Oral Contraceptives and the
Risk of Ovarian Cancer
1. What is the independent?
…………………………
2.What is the dependent variable?
………………………..
12

 Solution:
1.What is the independent variable?
Oral contraceptives
2.What is the dependent variable?
Ovarian cancer
13

 Confounding variable (confounder):
 An independent variable that distorts
the association between independent
and dependent variable
 It is related to both independent and
dependent variables.
15

 Is related to the exposure of interest
(although not causally) and causally
related to the out come.
 Is an unmeasured third variable
16

 Conditions for a factor to be
a confounder:
 Must be an independent risk factor for
the outcome(disease)
 Must be associated with the risk
factor(exposure) .
 Must not be an intermediate step in the
causal path
18

19
risk factor
(exposure)
out come
Confounding
variable
Cause
Non Cause

20
Smoking
(risk factor/
exposure)
Lung cancer
(out come)
Mining
(Confounding
variable )

21
Bottle feeding
(risk factor/
exposure)
diarrhea
(out come)
Mother
education
(Confounding
variable )

 How to identify confounding
variables?
 Background variables such as age,
gender, education, economic status, and
religion are confounders, because they
are related to many aspects of life.
22

 Known confounding variables from the
literature should be taken into
consideration, while others can be
identified by intensive thinking about the
possible risk factors
23

Exercise
 Determine the type of variable:
1. Weight (1 kg, 1.5 kg, 1.9 kg)
2. Disease Outcome (full recovery, chronic
illness, death)
3. Number of visits to a clinic (0, 1, 2, 3, 4)
4. Height (0.9 cm, 1 cm, 1.7 cm)
5. Gender (male, female)
24

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