Research Methods and Bias in Studies

The assignment delves into the critical concepts of bias in research methodologies. Students analyze case studies examining selection and measurement biases, focusing on factors like confounding variables and response rates. They are tasked with identifying potential biases in a study about drug use among students and proposing strategies to mitigate these issues.

Running head: EPIDEMIOLOGICAL ANALYSIS
The University of Western Sydney
School of Science and Health
Introduction to Epidemiology (401076)
ASSIGNMENT 2
Autumn, 2016
Due date: 24 September, 2017 midnight or 11:59PM
This assignment is based on the learning objectives and concepts in weeks 3-7, but may also
require knowledge from Topic 1st and 2 week. There are a total of 50 marks and this
assignment will contribute 30% towards the total assessment for this subject.
Your assignment should be typed, with 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. No answers need to be longer than a few short
sentences or short paragraphs. Please note this is an individual exercise.
Re-submission will not be permitted.
Late assignments will not be accepted without prior approval- use special
consideration e-form
Save your assignment as follow
Family name_first name_SID_Ass2

1EPIDEMIOLOGICAL ANALYSIS
Assignment Cover Sheet
School of Science & Health
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Unit name and number: 401076
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2EPIDEMIOLOGICAL ANALYSIS
Epidemiological analysis
Name of the student:
Name of the University:
Author Note:

3EPIDEMIOLOGICAL ANALYSIS
Table of Contents
Question 1: 3
Question 2: 6
Question 3 9
Question 4: 11
Question 5: 11
Question 6: 12
Question 7: 12
Bibliography: 13

4EPIDEMIOLOGICAL ANALYSIS
Question 1:
(a) “What study design does this study employ”?
The study design of this research article is qualitative cohort study.
(b) “Find the methodological aspects mentioned in the paper that convinced you that is the type
of study design, please use dot points”
 The data collection for the research study had used qualitative data.
 The data collection method employed was interview.
 The data analysis method utilized had been statistical analysis.
(c) “What justification do the authors give for conducting this study, please use dot points”?
 Authors propose that there is a significant interdependency between the physical
inactivity and low socio- economic status in case of coronary heart diseases.
 They also argue that there has not been enough attention to the women of low SES
and risk of CHD.
 Their study reduces bias and includes both men and women considering physical
inactivity and its association with the CHD, which had not been done before.
d) “What was the proportion of those who (i) do not do any physical activity (ii) engaged in
twice a week vigorous physical activity”?
i. 9% of the people
ii. 42.3% of the people

5EPIDEMIOLOGICAL ANALYSIS
(e) “What is the crude incidence rate of CHD in inactive men and inactive women”?
111 and 38 per 10,000 person years respectively.
(f) “What is the crude relative risk of being non-active versus being “highly active” (vigorous
physical activity at least twice a week) in men and in women”
0.50
(g) “How would you interpret the relative risk in the above section”
The relative risk ratio is calculated by comparing two critical factors, the comparison by two
exposure variables with the exposure denominator for each exposure group.
Now increase in the amount of physical activity can active reduce the risk factor for attaining
CHD in the future, as physical activity lowers blood pressure and does not let excess lipid to be
stored within the body, the relative risk for CHD will be based on the increasing level physical
activity in the respondents.
(h) “Looking at the sex and age adjusted RR in Table 3 (the RR is measured by the Hazard Ratio
which is similar) (i) how would you describe the association between physical activity and
CHD”

6EPIDEMIOLOGICAL ANALYSIS
As per the sex and age adjusted RR (measured by HR ratio), the variable for the individuals
who never engaged in physical activity is 1, which is the highest references number. With the
increasing incidence of physical activity the relative risk continued to decrease. The ratio of
people engaging in physical activity occasionally remained 0.72, which is lower than the ones
never engaging in physical activity but is still comparatively higher. The people who participated
in physical exercise once to twice a week, their RR had been 0.64, which is considerably lower
when compared to the rest of the two variables mentioned. It indicates clearly at the direct
association with physical inactivity in an adversely proportional fashion. In case of people
engaging in physical activity vigorously at least twice a week, had the lowest relative risk of
CHD, at 0.46; which is lesser than half of the relative risk for people not doing physical activity
as all. Hence it can be stated that CHD risk factor is intricately linked with lack of adherence to
regular physical activity.
(i) “The authors removed from the analysis any person who self-rated their health as “bad” or
“anywhere between good and bad” why?
The authors removed any personnel who responded about health as being “bad” or
‘anywhere between good or bad” because it was interpreted that they have poor self rated health
conditions, and had the potential to influence the results of the study.
(j) “What possible bias could have changed the estimate for the association between physical
activity and CHD – mention at least one, and explain why”

7EPIDEMIOLOGICAL ANALYSIS
A considerable bias that had the potential to influence the results of the study altering the
interconnection between the physical inactivity and incidence of Coronary heart disease is
limitation posed by some disease or disability. It has to be understood that disability can often
restrict the mobility of an individual and such a person will not be able to engage in regular or
periodic physical activity sessions, and will inevitably he at high risk of coronary heart disease.
In case of diseases that restrict excessive physical exhaustion it will also increase the risk of
CHD; hence, the factor of physical delimitation can be a significant factor that could have
incorporated bias into the research study under consideration.
(k) “Do you think this research adequately addressed confounders? Justify your answers.”
The confounding factors to this research study like age, sex, SES, smoking history, BMI
were all included and adjusted in the research study to address the influential impact of these
factors on the result of the research study. However, some confounders like people who self-
rated their health as bad or average, or people who have restricted motility due to disability or
disease process were completely excluded from the study to avoid bias. Hence it can be stated
that the researchers of this article could address all confounders.
Question 2:
a) What is the study design, justify?
The study design for this research study is exploratory cohort analysis study. It can be
justified by the sampling a population of 2 million women belonging to different socio-
economic statuses, dependent upon whether they have taken Reserpine or not.
b) Build the 2X2 table consist with data above. To be able to fill in the cells you have to
assume that there is no association between the use of Reserpine and breast cancer. In

8EPIDEMIOLOGICAL ANALYSIS
other word the prevalence of breast cancer is similar among drug users and non-drug
users and this is true in both high and low SES. Hint: to help you fill in the data you must
start with the number that appears in the Table marginal total columns and rows.
High SES Low SES
Brea
st
Canc
er
No
breast
cancer
Total Breast
Cancer
No
breast
cancer
Total
Use
Reserpi
ne.
16 7998
4
80,000 4 19996 20,000
Non-
users of
Reserpi
ne
184 9198
16
920,00
0
196 97980
4
980,00
0
Totals 200 999,8
00
1,000,0
00
200
per
10000
00
200
per
10000
00
1,000,0
00
Now assume that the association with Reserpine was evaluated in a follow up study and the
investigators found that the incidence rate of breast cancer among women who used

9EPIDEMIOLOGICAL ANALYSIS
Reserpine was 3 times higher than among women who did not use Reserpine. Stratum
specific analysis showed that this was true for both high and low SES.
If Reserpine is causally related to breast how many cases of breast-cancer could be avoided
in the high SES and Low SES had Reserpine would be banned from being in the market? (In
other words what is the PAF?)
Assuming the above mentioned fact, the table calculated:
Breast
Cancer
No breast
cancer
Total
Use
Reserpine.
552 79448 80,000
Non-users
of
Reserpine
184 919816 920,000
Totals 736 999,264 1,000,000
R.R=
552
80,000
184/920000
=345
P.A.F=
80,0000
92,0000 (345−1)
80,000
92,0000 ( 345−1 ) +1
=0.96

10EPIDEMIOLOGICAL ANALYSIS
Interpretation:
96% of the women taking Reserpine are attributed to breast cancer according to the given
assumptions.
Question 3
A new drug to lower blood pressure (BP) is being tested. The results of the RCT are
displayed below:
Exposure
There was a speculation, that the drug may not be as effective in overweight individuals as in
normal weight. The results was stratified by weight status and are presented bellow.
Over-weight Normal weight
BMI >= 25 BMI <25
Lowered No
change
Lowered No
change
Lowered
BP
No
change
in BP
Drug 70 30 100
Placebo 40 60 100

11EPIDEMIOLOGICAL ANALYSIS
BP in BP BP in BP
Drug 30 20 Drug 40 10
Placebo 20 30 Placebo 20 30
a) Calculate the crude measure of association between the drug and blood pressure
According to the data represented in the case controlled study, the risk ratio
calculated for the total sample was 1.79, which is known as the crude measure of association
between the variables; however, it also needs to be taken into account that this RR was not
adjusted with the confounding factors. The risk ratio or RR for those with BMI higher than
25 was less than the standard crude ratio calculated, and the RR for the respondents who had
BMI lesser than 25, had crude ratio higher than the standard one.
b) Calculate the stratum specific association between the drug and blood pressure.
The stratum specific risk ratios are as follows:-
Among those with BMI>=25, the risk ratio is:
RR= 30/50
20/50 = 1.5
Among those with BMI< 25, the risk ratio is:
RR= 40/50
20/50 = 2
c) Interpreted your findings.

12EPIDEMIOLOGICAL ANALYSIS
As per the results calculated it can be interpreted that the speculation hypothesize in the
study had proven to be correct as the risk ratio for those with higher BMI are having greater
risk of higher BP and those with normal BMI are having lower risk of elevated blood
pressure. Hence, it can be concluded that the drug being tested in the study is far more
effective in people with normal body weight as compared to the obese ones.
Question 4:
Could this difference induce a bias?
Yes this difference can induce a bias; this kind of bias is known as observational selection
bias. In order to explain more, it can be said that the consideration of more number of men in the
study has high potential to have altered the results in some way or the other.
What would be a practical way to avoid such differences in case control studies?
Selection bias can be actively avoided by either establishing convenient sampling method or
by ensuing well matched sampling frames with the target population.
Question 5:
Which of the following terms associated with selection bias?
b. Confounding
Explain your choice in one sentence.
Confounding actors or confounders can be defined as the variables that influence the
outcome of the results by wither overestimating or underestimating the intervention, confounders
are associated with sampling errors and they induce mostly type 1 or type 2 errors.

13EPIDEMIOLOGICAL ANALYSIS
Question 6:
Which of the following term is associated with measurement bias?
c. Response rate.
Explain your choice in one sentence.
Response rate is intricately linked with measurement bias, and it incorporated bias when the
rate of non response is not equally distributed among all the respondents or participants of the
research study altering the outcome of the study.
Question 7:
As the research is based on discovering the drug use rate among the students, the most
probable bias for this situation can be the non responsive bias. As the concept of drug abuse is
not only confidential but also illegal in most cases, the students might refuse to respond
altogether, or might respond with faulty or incomplete data. Hence, it will incorporate a
significant alteration in the study design and the outcome of the study serving to be a huge
selection bias.

14EPIDEMIOLOGICAL ANALYSIS
Bibliography:
Eom, C. S., Park, S. M., & Cho, K. H. (2012). Use of antidepressants and the risk of breast
cancer: a meta-analysis. Breast cancer research and treatment, 136(3), 635-645.
Sundquist, K., Qvist, J., Johansson, S. E., & Sundquist, J. (2005). The long-term effect of
physical activity on incidence of coronary heart disease: a 12-year follow-up study.
Preventive medicine, 41(1), 219-225.