GTB225
Answer for Tutorial 3 and 4
June 2020
Matric No: 141793
Name: MUHAMMAD SYABIL SYAUQI BIN ISHAK
Program: KPP
Question
1
a
Answer
Rate ratio
=
=
𝐂𝐮𝐦𝐮𝐥𝐚𝐭𝐢𝐯𝐞 𝐢𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐢𝐧 𝐬𝐦𝐨𝐤𝐞𝐫𝐬
𝐂𝐮𝐦𝐮𝐥𝐚𝐭𝐢𝐯𝐞 𝐢𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐢𝐧 𝐧𝐨𝐧−𝐬𝐦𝐨𝐤𝐞𝐫𝐬
9/719
31/2737
= 0.0125/0.0113
= 1.11
The smokers those smoking 0.5 pack of cigarettes per day will 1.11 times the
risk to get myocardial infarction than non-smokers.
b
Rate ratio
=
=
𝐂𝐮𝐦𝐮𝐥𝐚𝐭𝐢𝐯𝐞 𝐢𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐢𝐧 𝐬𝐦𝐨𝐤𝐞𝐫𝐬
𝐂𝐮𝐦𝐮𝐥𝐚𝐭𝐢𝐯𝐞 𝐢𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐢𝐧 𝐧𝐨𝐧−𝐬𝐦𝐨𝐤𝐞𝐫𝐬
39/1864
31/2737
= 0.0209/0.0113
= 1.85
The smokers those smoking 1 pack of cigarettes per day will 1.85 times the risk
to get myocardial infarction compared to non-smokers.
c
Rate ratio
=
=
𝐈𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐫𝐚𝐭𝐞 𝐢𝐧 𝐬𝐦𝐨𝐤𝐞𝐫𝐬
𝐈𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐫𝐚𝐭𝐞 𝐢𝐧 𝐧𝐨𝐧−𝐬𝐦𝐨𝐤𝐞𝐫𝐬
18/623
31/2737
= 0.0289/0.0113
= 2.55
The smokers those smoking 2 packs of cigarettes per day will 2.55 times the risk
to get myocardial infarction compared to non-smokers.
GTB225
2
a
Answer for Tutorial 3 and 4
June 2020
The possible confounding factors should be taken into consideration if the
comparison group was of the same age and sex are social background, heredity and
poor nutritional status.
b
The suitable comparison group can be the people that come from similar ethnic and
social background. For example, we can take the family member such as brother and sister
of the exposed children to become a comparison group.
3
a
Odds ratio
=
=
𝐎𝐝𝐝𝐬 𝐭𝐡𝐚𝐭 𝐚 𝐜𝐚𝐬𝐞 𝐞𝐱𝐩𝐨𝐬𝐞𝐝
𝐎𝐝𝐝𝐬 𝐭𝐡𝐚𝐭 𝐚 𝐜𝐨𝐧𝐭𝐫𝐨𝐥 𝐞𝐱𝐩𝐨𝐬𝐞𝐝
30/17
134/81
= 1.7647/1.6543
= 1.07
Alcohol drinker who have a number of drinks per day = 1 ,will 1.07 times the
risk to get breast cancer compared to non-alcohol drinker.
b
Odds ratio
=
=
𝐎𝐝𝐝𝐬 𝐭𝐡𝐚𝐭 𝐚 𝐜𝐚𝐬𝐞 𝐞𝐱𝐩𝐨𝐬𝐞𝐝
𝐎𝐝𝐝𝐬 𝐭𝐡𝐚𝐭 𝐚 𝐜𝐨𝐧𝐭𝐫𝐨𝐥 𝐞𝐱𝐩𝐨𝐬𝐞𝐝
45/17
163/81
= 2.6471/2.0123
= 1.32
Alcohol drinker who have a number of drinks per day = 2 , will 1.32 times the
risk to get breast cancer compared to non-alcohol drinker.
c
Odds ratio
=
=
𝐎𝐝𝐝𝐬 𝐭𝐡𝐚𝐭 𝐚 𝐜𝐚𝐬𝐞 𝐞𝐱𝐩𝐨𝐬𝐞𝐝
𝐎𝐝𝐝𝐬 𝐭𝐡𝐚𝐭 𝐚 𝐜𝐨𝐧𝐭𝐫𝐨𝐥 𝐞𝐱𝐩𝐨𝐬𝐞𝐝
40/17
130/81
= 2.3529/1.6049
= 1.47
GTB225
Answer for Tutorial 3 and 4
June 2020
Alcohol drinker who have a number of drinks per day = 3 + , will 1.47 times the
risk to get breast cancer compared to non-alcohol drinker.
4
a
b
Cohort Studies
I.
Exposed workers
Incidence = 40/2500 X 10, 000
= 160
= The incidence of brain cancer in exposed workers are
=================160 per 10,000 population
II.
Unexposed workers
Incidence = 60/7500 X 10, 000
= 80
= The incidence of brain cancer in unexposed workers are
=================80 per 10,000 population
III.
All workers combined
Incidence = 100/10,000 X 10, 000
= 100
= The incidence of brain cancer in all workers combined
=================are 100 per 10,000 population
c
Relative risk/risk ratio =
𝐈𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐢𝐧 𝐞𝐱𝐩𝐨𝐬𝐞𝐝 𝐰𝐨𝐫𝐤𝐞𝐫𝐬
𝐈𝐧𝐜𝐢𝐝𝐞𝐧𝐜𝐞 𝐢𝐧 𝐮𝐧𝐞𝐱𝐩𝐨𝐬𝐞𝐝 𝐰𝐨𝐫𝐤𝐞𝐫𝐬
Incidence rate in the exposed group = (40/2500)
Incidence rate in the unexposed group = (60/7500)
Relative risk = (40/2500) x (60/7500)
= 2 times the risk
The workers who exposed to the herbicide will 2 times the risk to develop brain
cancer compared to workers who do not exposed to the herbicide.
d
Rate difference = incidence in exposed-incidence in unexposed
GTB225
Answer for Tutorial 3 and 4
June 2020
Rate difference = 40 – 60
= - 20
5
Sensitivity = a/(a +c)
= [60/ (60+20)] X 100
= 0.75×100
= 75%
Specificity = d/(b +d)
= [80/(80+40)] X 100
= 0.67 ×100
= 66.7%
True disease test
6
Screening
result
a
No Breast
cancer
796
Total
Positive
Breast
cancer
190
Negative
10
39,004
39,014
Total
200
39,800
40,000
986
Sensitivity = [190/ (190+10)] X 100
= 0.95 ×100
= 95%
There were 95% probability that the screening test/result will be positive if
young women have risk to develop breast cancer
b
Specificity = [39004/(39004+796)] X 100
= 0.98 ×100
= 98%
There were 98% probability that the screening test/result will be negative if
young women have no risk to develop breast cancer
c
Negative predictive value, PV- =
(39004)
(39014)
x 100 %
= 99.97 %
There were 99.97 % probability of not having a breast cancer when the result
of the test is negative.
d
Positive predictive value, PV+ =
(190)
(986)
x 100 %
GTB225
Answer for Tutorial 3 and 4
June 2020
= 19.27 %
There were 19.27 % probability of having a breast cancer when the result of
the test is positive.
True disease test
7
Sinusitis
X-ray result
a
Positive
49
No
Sinusitis
79
Total
Negative
46
73
119
Total
95
152
247
128
Sensitivity = [49/ (49+46)] X 100
= (49/ 95) × 100
= 51.58%
b
Specificity = [73/(73+79)] X 100
= (73/152) × 100
= 48.03%
c
Positive predictive value, PV+ =
=
49
(49+79)
49
x 100 %
x 100 %
128
= 38.28 %
d
Negative predictive value, PV- =
=
73
(73+46)
73
119
x 100 %
x 100 %
= 61.34 %
e
Proportion (%) of sinusitis=
𝐓𝐨𝐭𝐚𝐥 𝐧𝐮𝐦𝐛𝐞𝐫 𝐨𝐟 𝐜𝐚𝐬𝐞𝐬
𝐓𝐨𝐭𝐚𝐥 𝐏𝐨𝐩𝐮𝐥𝐚𝐭𝐢𝐨𝐧 𝐚𝐭 𝐫𝐢𝐬𝐤 𝐚𝐭 𝐭𝐡𝐞 𝐭𝐢𝐦𝐞 𝐩𝐞𝐫𝐢𝐨𝐝
==
=
(49+46)
95
247
247
x 100 %
x 100 %
=38.46 %
x 100 %