Epidemiology Assignment 2: Study Design, Exposure, Outcome, Bias, and Association

Introduction to Epidemiology (401076)
ASSIGNMENT 2
Spring, 2019
Due date: Midnight (11:55PM), 29 September 2019
This assignment is based on the learning objectives and concepts in Weeks 4-8, but
may also require knowledge from previous weeks as the knowledge is accumulated.
There are a total of 66 marks and this assignment will contribute 30% towards the
total assessment for this subject.
Your answers should be typed in the space provided between the questions! Don’t
erase the questions as there is adequate space left between questions.
Assignments should be submitted via vUWS (see specific instructions relating to
Assignment 2 on the 401076 vUWS web-site). Be as brief as possible in your
answers, and use the number of marks for a question as a guide to how much to write.
No answers need to be longer than a few short sentences or short paragraphs. Please
note this is an individual exercise.
Late assignments will not be accepted without prior approval.
Remember to save your assignment to make sure it is the final version and
submit only this. as:
Family name_First name_StudentID_Ass2_final

Question 1: [26]
Read the following paper, and answer the questions below: “Vo TM, Tran VTN, Cuu
TNT, Do TTH, Le TM. Domestic violence and its association with pre-term or low
birthweight delivery in Vietnam. International Journal of Women Health 2019:11
501–510”
(a) “What study design does this study employ and identify from the paper
methodological features that support the design you just noted ?” [2 mark]
The chosen design of this study is cross-sectional study where the participants were
interviewed with a structured interview questionnaire. The sampling strategy used in
this research is random sampling.
(b) “What is/are the main exposure/s and what is/are the main outcome/s of this study
in operational terms (i.e., you answer should include how the measure was defined)?”
[4 marks]
The main exposure of this study was the experiencing domestic violence during
pregnancy period. The domestic violence has been measured by their experience of
physical violence, sexual violence and emotional violence considering measurable
scale.
The main outcome of this study is pre-term delivery or low birth weight of the child.
It has been measured by binary scale (Yes/No). Low birth weight considered for the
newborn with less than 2500 gram weight.
(c) “Do you think the risk of selection bias is high or low? Your answer should be
justified by no more than 60 words!! Too long answer will be penalised ?” [4
marks]
The selection bias in this study is very low. The potential cause of selection bias in
this case would be the economic and social bias of the chosen districts and local areas
around the hospitals. In this case, the chosen hospitals are accessible by people
diverse economic and demographic. Hence, the possibility of selection bias is very
low.
(d) “Compute the crude OR for domestic violence (yes/no) and pre-term/low
birthweight from data presented in Table 4 and interpret this in your own words.” [4
mark]

Pre-term/low
birthweight Yes
Pre-term/low
birthweight No
Total
Domestic Violence
Yes
54 203 257
Domestic Violence
No
106 736 842
Total 160 939
OR=
case∈exposure group
control∈exposure group
case ∈nonexposure group
control∈nonexposre
=
54
203
106
736
= 54 x 736
203 x 106 =1.847
From the above crude odd ratio it has been found that the odd ratio is approximately
1.8 which is very high than 1. Therefore, significance association has been found
between domestic violence and pre-term birth and low birth weight.
(e) “Was the crude OR differ from the adjusted and if yes why? if no why?” [4
marks]
The crude odd ratio is significantly different than the adjusted odd ratio. The reason
behind this difference is the influences of other confounder variable on research
outcomes. There are other confounding variable or exposures such as economic
status, wife’s age group and husband’s alcohol abuse that also influence the odds of
domestic violence in per-term/low birth rate.
(f) “What was the prevalence of physical violence in this sample and what was the
adjusted prevalence odds ratio (POR-Table 5) between physical violence and pre
term/low birthweight? Interpret the association in your own words, could it be a result
of some error?” [4 marks, no more than 100 words]
Prevalence of physical violence is PP= number of total exposure
number of total participants =
13+ 67
147+872 =0.072and adjusted prevalence odds ratio between physical violence and
pre term/low birthweight 0.69
The prevalence of physical violence has been calculated through considering the total
number of physical valance and total number of sample size. However, the prevalence
odd ratio is the result of ratio of odds in exposure and non-exposure group. This
caused the difference between the two results.