Study Variables (3).pdfStudy Variables (3).pdf

Study Variables (3).pdf

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STUDY VARIABLES

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Outline
nWhat are variables?
nWhat are the different types of variables?
nDistinguish between dependent and
independent variables

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Variables
nA variable is the characteristic (of a person,
object or phenomenon) that can take on
different values
nIt may change (as opposed to Constants) in
the same person at different times or it varies
from person to person at the same time
nIt is the data needed to meet the objectives of
the study

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Examples of Human Variables
nColour
nAge
nWeight
nAttitudes
nKnowledge
nPractices etc

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Examples of Health Unit Variables
nLocation
nBed capacity
nNumber of staff
nBed occupancy

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Variables in Research
nAre the factors under study

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Where do we get variables from?
nAre (should be) contained in the objectives
nAre derived from the problem analysis
diagram
–The factors assumed to cause or influence the problem
nMay also be derived from topic

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Variables
Variables
nWaiting time
nAvailability of
drugs
nFrequency of
supervision

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nTo determine the socioeconomic factors
that influence teenage in..
nTo identify socio-demographic factors…
Variables from Objectives

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Variables from Objectives
nTo assess household knowledge, attitudes and
practices towards fever in children
nTo establish the quality of services rendered to
the patients
nTo find out the measures in place for
occupatio²€health and safety at Kajjansi Clays
Factory

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Variables from Objectives
nTo establish the types of waste produced at each of
the hospitals
nTo describe the health care infrastructure per district
with respect to maternal health care

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Operationalising Variables
nVariables may be confusing unless they
are operationalised
nThey may have many interpretations
nOperationalising variables means making
them distinct and measurable
–Give each variable an operational definition

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Operationalising Variables
nThe values of some variables can easily
be determined, e.g.
–Age: 2months., 3 years, young, old, etc
–Sex: male, female: Sex= Female
nThe values of some other variables may
not be measured directly, e.g.
–Level of knowledge, nutritional status

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INDEPENDENT AND DEPENDENT VARIABLES
nIndependent Variables:
–Used to measure or describe the factors presumed to cause or
influence the development of the problem
–Controlled by the researcher in an experiment e.g. dose esp for
experimental studies
nDependent Variables:
–Used to measure or describe the problem under study
–Results from interaction of the independent variable with the
subject under study
–Describes the presumed or observed effect of intervention
–Consequent

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Dependent Variables
nDescribes “outcomes” which are
dependent on “exposures” (independent
variables)
nE.g. in a study of the relationship between
smoking and lung cancer, “suffering from
lung cancer” is the dependent variable
because smoking takes place before the
development of the cancer.

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Independent Variables
nDescribes “exposures” or interventions to which
a study group is subjected or assigned
nResults in an effect or outcome (described by
the “dependent” variable)
nE.g. in a study of why people smoke, “smoking”
is the dependent variable and a factor like “peer
pressure” is the independent variable

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Other Types of Variables
nConfounding Variables (intervening and
moderating) :
–Is an Independent variable associated with both the
Outcome and the possible Cause
–May confuse (= confondre (fr.) = confuse)
–May strengthen or weaken the apparent relationship
between a problem and its possible cause
–May distort relationship between factor and problem
(suggest preventive effect or implicate innocent
factor)
–Should demonstrate a triangular relationship and not
intervene in between

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Confounding Variables (int. & mod.)
Cause
(Independent
Variable)
Effect / Outcome
(Dependent
Variable)
Other Factors
(Confounding
Variables ( int,
mod)

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Confounding Variables
Mother’s Education
(Independent
Variable)
Malnutrition
(Dependent
Variable)
Family Income
(Confounding
Variables)

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Confounding Variables
nIn a study of an outbreak of Topical Epidermal
Necrolysis (TEN) among young women, it was
found that all the women who suffered from TEN
had
–Employment as secretaries
–Used red lipstick in the week preceding illness
–Used Rely
® sanitary pads in the week preceding illness
–Ate vanilla ice-cream in the week preceding illness
nWhich of the above factors could have caused
the illness and which could have been the
confounder?

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Background Variables
nAre some variables that are related to the
IV and influence the outcome indirectly
e.g. Age, Sex, Socio-economic status,
Marital Status, Religion etc
nUsually become confounders
nLimit their measurement during the study

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Exercise
na) As District Health Inspector, you believe that
anaemia, malaria and malnutrition are serious
problems in your district, especially in adult male
farmers. You wish to study the prevalence of the
problems in adult males of different ages,
occupations and education.
nWhat are your
–Independent Variables?
–Dependent Variables?
Qn b) Construct a conceptual framework for your variables

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Variables End
n Thank you!
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