Non experimental designs Flashcards
name the 3 types of non experimental design
1) Descriptive correlational study
2) Case-control study
3) Cohort study
what is cohort study?
It refers to ‘‘any
designated group of individuals who share
a common experience or condition”
It defines two or more groups of people that are free
of disease at the beginning but differ on their
exposure (e.g. smoking status) to a potential
causes of the diseases.
what does cohort study investigate?
it investigates the etiology of disease based on one’s exposure to toxic/ carcinogenic substances.
define exposed cohort
individuals experienced the
putative causal event or condition (i.e. smokers)
define reference cohort
Reference cohort – individuals thought of
unexposed to the condition (i.e. non-smokers)
what is the most straightforward type of epidemiologic study?
cohort study
what is the primary goal of cohort study?
to measure and usually to
compare the incidence of disease or
event in the study cohorts.
Name the 4 types of cohort studies:
1)prospective cohort
2)retrospective cohort
3)ambi-directional cohort
4) nested case control
what is prospective cohort?
it is looking forward, likely to happen in the future.
defines a sample and predictor
variables before any outcomes (diseases)
have occurred and then collect the data for
the study in a prospective manner
name 4 strengths of prospective study:
1) Able to control how to measure the exposure
2) Able to measure confounding variables
3) Avoid recall bias
4) Able to calculate relative risk for the outcome
what are 2 weaknesses of cohort study?
1) costly
2) lengthy
what is retrospective cohort?
it takes effect from the past.
defines a sample and predictor variables after
outcomes (diseases) have occurred. The
data basically exists and the investigators
use the data to answer the questions in
interest.
examples:
A retrospective cohort study on the risk of obesity among
shift workers
A retrospective cohort study of the Nagasaki atomic bomb
survivors for the risk of preleukemia.
what are the 3 strengths of retrospective cohort study?
1) Inexpensive
2) Time-saving
3) Able to study longitudinally with long latent periods
what are the 4 weaknesses of retrospective studies?
1) Risk of confounding variables - cannot measure as data has been collected
2) Sometimes unable to determine exact exposure
- unable to use an exact scale
3) Measurement error
4) Selection bias
- unable to control how participants of primary data were selected for inclusion
what is ambi directional cohort?
combination of retrospective and prospective to gain more information to help answer the question.
1 Strength for Ambi-directional cohort study
Captures exposures that can cause both short-term &
long-term outcomes
3 Weaknesses of ambi-directional cohort study
1) Costly and lengthy
2) Risk of confounding variables
3) Exposure determination problems
define risk for cohort study analysis
Risk is defined as the probability that an event occur and
it is measured as incidence rate (IR) in cohort study
What is rate ratio/ risk ratio/ relative risk.
Define as the
ratio between the incidence rates of the two groups,
can be used to compare the risk in the two groups:
RR=IR E /IRNE
what is the purpose of descriptive study?
To observe, describe and document aspects of a
situation
what is the purpose of descriptive correlational study
To examine a relation between variables without
attempting to infer causal relationship
what are the 5 methods of analysis for simple descriptive study?
Descriptive statistics like
mean,
standard deviation,
median,
frequency,
percentage, etc.
what are the 4 methods of analysis for descriptive correlational study?
Descriptive correlational study –
Pearson’s
correlation,
Spearman’s rank correlation,
regression,
logistic regression, etc.
