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BIOLOGY, M8 2025 HSC 13 MC

The prevalence of a non-infectious disease has remained constant for over 10 years. A new treatment for this disease prolongs the life of people with the disease, but does not cure them.

Which row in the table shows the effect of the treatment on both the incidence and prevalence of this disease?

\begin{align*}
\begin{array}{l}
\rule{0pt}{2.5ex} \ \rule[-1ex]{0pt}{0pt}& \\
\rule{0pt}{2.5ex}\textbf{A.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{B.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{C.}\rule[-1ex]{0pt}{0pt}\\
\rule{0pt}{2.5ex}\textbf{D.}\rule[-1ex]{0pt}{0pt}\\ 
\end{array}
\begin{array}{|l|l|}
\hline
\rule{0pt}{2.5ex}\textit{Change in incidence}\rule[-1ex]{0pt}{0pt}& \textit{Change in prevalence} \\
\hline
\rule{0pt}{2.5ex}\text{None}\rule[-1ex]{0pt}{0pt}&\text{Increases}\\
\hline
\rule{0pt}{2.5ex}\text{None}\rule[-1ex]{0pt}{0pt}& \text{Decreases}\\
\hline
\rule{0pt}{2.5ex}\text{Increases}\rule[-1ex]{0pt}{0pt}& \text{None} \\
\hline
\rule{0pt}{2.5ex}\text{Decreases}\rule[-1ex]{0pt}{0pt}& \text{None} \\
\hline
\end{array}
\end{align*}

Show Answers Only

\(A\)

Show Worked Solution
  • A is correct: Treatment doesn’t affect new cases but increases prevalence by prolonging life.

Other Options:

  • B is incorrect: Prolonging life increases prevalence, not decreases it.
  • C is incorrect: Treatment doesn’t cause more new cases to occur.
  • D is incorrect: Treatment doesn’t prevent new cases from occurring.

BIOLOGY, M8 2024 HSC 29

An epidemiological study was conducted to help model how many people will be affected by Type 2 diabetes globally in the future. Continuous data were collected from 1990 to 2020. From that data, the following data points were chosen to demonstrate the trend.

\begin{array} {|c|c|}
\hline
\rule{0pt}{2.5ex} \textit{Year} \rule[-1ex]{0pt}{0pt} & \textit{Percentage of population affected} \\
\rule{0pt}{2.5ex} \textit{} \rule[-1ex]{0pt}{0pt} & \textit{by Type 2 diabetes (%)} \\
\hline
\rule{0pt}{2.5ex} \text{1990} \rule[-1ex]{0pt}{0pt} & \text{3.1} \\
\hline
\rule{0pt}{2.5ex} \text{2000} \rule[-1ex]{0pt}{0pt} & \text{3.7} \\
\hline
\rule{0pt}{2.5ex} \text{2010} \rule[-1ex]{0pt}{0pt} & \text{4.3} \\
\hline
\rule{0pt}{2.5ex} \text{2010} \rule[-1ex]{0pt}{0pt} & \text{5.6} \\
\hline
\end{array}

  1. Plot the data on the grid provided and include the line of best fit.   (2 marks)
     

  1. A prediction of the global population numbers suggests there will be about 9 billion \((9\ 000\ 000\ 000)\) people on the planet by 2040.

    Predict the number of people that will be affected by diabetes in 2040. Show working on your graph on the previous page and your calculations.   (3 marks)

Show Answers Only

a.   

b.   630 000 000 (630 million)

Show Worked Solution

a.   

♦ Mean mark (a) 56%.

b.   Using the LOBF on the graph:

Population (%) with diabetes in 2040 = 7%

People with diabetes in 2040 = \(\dfrac{7}{100} \times 9\ 000\ 000\ 000 = 630\ 000\ 000\)

BIOLOGY, M8 2024 HSC 17 MC

Over 12 months, the prevalence of a non-infectious disease will increase in a population if

  1. the total population increases.
  2. disease recovery time decreases.
  3. the incidence rate of the disease decreases.
  4. the survival time of individuals with the disease increases.
Show Answers Only

\(D\)

Show Worked Solution
  • Prevalence = number of existing cases in a population at a given time.
  • Factors affecting prevalence include new cases (incidence), duration of disease, death/recovery rates and population changes.
  • If people with the disease live longer, they remain in the “prevalent cases” count for a longer time, increasing overall prevalence.

\(\Rightarrow D\)

♦ Mean mark 51%.

BIOLOGY, M8 2024 HSC 11 MC

The data shows the proportion of adults living in Australia who are obese.
 

Which of the following can be observed from the data?

  1. The proportion of obese adults always increases with age.
  2. There is a greater percentage of men who are obese than women in all age groups.
  3. The proportion of women who are obese increases from 13% at 18–24 to 38% at 65–74.
  4. The proportion of men who are obese increases from 18% at 18–24 to 35% at 45–54, then decreases to 23% at age 85 and over.
Show Answers Only

\(C\)

Show Worked Solution
  • Options \(A, B\) and \(D\) can be shown to be incorrect with reference to the table.

\(\Rightarrow C\)

BIOLOGY, M8 2023 HSC 16 MC

Mesothelioma is a non-infectious environmental disease caused by exposure to asbestos. The table shows the number of new cases, existing cases and deaths caused by Mesothelioma in Australia in 2020.
 

  New Cases Existing cases -
five year survival		 Deaths
Males 499 801 590
Females 143 239 206
Total 642 1040 796

 
In 2020 the Australian population was 26 million.

What is the incidence rate for Mesothelioma in 2020 as a percentage?

  1. 0.000025%
  2. 0.000040%
  3. 0.0025%
  4. 0.0040%
Show Answers Only

\(C\)

Show Worked Solution
\( \text{Incidence}\) \( =\dfrac{\text{new cases} }{\text{population}} \)  
  \(=\dfrac{642}{26\ 000\ 000} \)  
  \(=0.000025 \times 100\text{%} \)  
  \(= 0.0025\text{%} \)  

 
\(\Rightarrow C\)

♦ Mean mark 52%.

BIOLOGY, M8 2019 HSC 33c

A large epidemiological study was conducted. It used historical data to investigate the association between Herpes simplex virus (HSV) infection and dementia. Dementia is caused by a variety of brain illnesses. Alzheimer's disease is the most common cause of dementia.

The study used the records of 8362 patients with HSV infection and 25086 randomly selected sex- and age-matched control patients without HSV infection. Some of the patients with HSV had been treated with antiviral medication.

The graph below shows some results of the study.
 

  1. Describe the trends shown in the data.   (3 marks)
Show Answers Only
  • The graph clearly shows that individuals with untreated HSV are at a greater risk of developing Alzheimer’s. While people without HSV or treated HSV remain relatively low up to 10 years, HSV patients can have 10 to 15 times the likelihood of developing Alzheimer’s, a trend which increases with age/time with HSV.
  • The treated HSV patients remain relatively low and almost identical to the individuals without HSV until 10 years where there is a sharp increase. However, it is still half the risk of untreated patients.
  • People without HSV have an incredibly low likelihood of obtaining Alzheimer’s, with only a very small increase in the 10 year follow up. 
Show Worked Solution

Data Trends:

  • The graph clearly shows that individuals with untreated HSV are at a greater risk of developing Alzheimer’s. While people without HSV or treated HSV remain relatively low up to 10 years, HSV patients can have 10 to 15 times the likelihood of developing Alzheimer’s, a trend which increases with age/time with HSV.
  • The treated HSV patients remain relatively low and almost identical to the individuals without HSV until 10 years where there is a sharp increase. However, it is still half the risk of untreated patients.
  • People without HSV have an incredibly low likelihood of obtaining Alzheimer’s, with only a very small increase in the 10 year follow up. 

BIOLOGY, M5 2019 HSC 33b

Alzheimer's disease causes destruction of brain tissue, dementia and eventually death.

The gene with the greatest known effect on the risk of developing late-onset Alzheimer's disease is called APOE. It is found on chromosome 19.

The APOE gene has multiple alleles, including e2, e3 and e4 .

  1.  What are multiple alleles?   (2 marks)

  2. The table shows the risk of developing Alzheimer's disease for various APOE genotypes compared to average risk in the population.
     

   

  1. Analyse the data to assess the risk of developing Alzheimer's disease associated with the e2, e3 and e4 alleles.   (4 marks)

Show Answers Only

i.     Multiple alleles

  • Alleles are the different variations of the same gene.
  • While most genes only have two alleles, dominant and recessive, some genes have 3 or more versions of itself. This phenomena is referred to as the gene having “multiple alleles”.

ii.  Analysis of data 

  • The table indicates that the alleles follow a hierarchy and have influence over the risk of Alzheimer’s, with certain combinations masking effects of others or amplifying them.
  • The e2 allele in both a homozygous genotype and coupled with e3 reduces the risk of Alzheimer’s by 40%. This suggests that the e2 allele is the one which reduces the risk of Alzheimer’s and can mask the effect of e3.
  • However, when coupled with e4, the risk of developing Alzheimer’s is 2.6 times more likely. This suggests that e4 is the more dominant allele.
  • The e4/e3 genotype also makes Alzheimer’s 3.2 times more likely in those individuals, and the e4/e4 genotypes makes it 14.9 times more likely. We can then make the conclusion that the e4 allele makes Alzheimer’s much more common in any genotype where it is present.
  • The e3 allele seems to be completely neutral and almost completely masked by both e2 and e4. In its homozygous genotype, it has no effect on the risk of developing Alzheimer’s, and when heterozygous with either e2 or e4, has little to no effect on the risk in comparison the e2 and e4’s homozygous genotypes.
  • It would then be accurate to conclude that the allele hierarchy is e3<e2<e4, with e3 being neutral and having no known effect, e2 reducing the risk of Alzheimer’s and e4 greatly increasing the risk of developing Alzheimer’s.
Show Worked Solution

i.     Multiple alleles

  • Alleles are the different variations of the same gene.
  • While most genes only have two alleles, dominant and recessive, some genes have 3 or more versions of itself. This phenomena is referred to as the gene having “multiple alleles”. 

♦♦♦ Mean mark (i) 24%.

ii.  Analysis of data 

  • The table indicates that the alleles follow a hierarchy and have influence over the risk of Alzheimer’s, with certain combinations masking effects of others or amplifying them.
  • The e2 allele in both a homozygous genotype and coupled with e3 reduces the risk of Alzheimer’s by 40%. This suggests that the e2 allele is the one which reduces the risk of Alzheimer’s and can mask the effect of e3.
  • However, when coupled with e4, the risk of developing Alzheimer’s is 2.6 times more likely. This suggests that e4 is the more dominant allele.
  • The e4/e3 genotype also makes Alzheimer’s 3.2 times more likely in those individuals, and the e4/e4 genotypes makes it 14.9 times more likely. We can then make the conclusion that the e4 allele makes Alzheimer’s much more common in any genotype where it is present.
  • The e3 allele seems to be completely neutral and almost completely masked by both e2 and e4. In its homozygous genotype, it has no effect on the risk of developing Alzheimer’s, and when heterozygous with either e2 or e4, has little to no effect on the risk in comparison the e2 and e4’s homozygous genotypes.
  • It would then be accurate to conclude that the allele hierarchy is e3<e2<e4, with e3 being neutral and having no known effect, e2 reducing the risk of Alzheimer’s and e4 greatly increasing the risk of developing Alzheimer’s.

♦♦ Mean mark (ii) 40%.

BIOLOGY, M8 2018 HSC 30

The graph shows the expected life span (the age to which people are expected to live in years) for people of different ages during the 20th century in one country.
 

There have been many biological developments that have contributed to our understanding of the identification, treatment and prevention of disease.

Evaluate the impact of these developments on the expected life span. In your answer, include reference to trends in the data provided.  (8 marks)

Show Answers Only
  • For all ages listed in the graph, life expectancy increased during the 20th century.
  • The lifespan from birth has increased more significantly than other ages ~ 48 to 74 years.
  • The smallest increase being for 60 year olds at ~ 5 years.
  • The ability to understand pathogens and the causes of infectious disease (Koch and Pasteur) has led to early identification and treatment of childhood illnesses such as rubella, polio and whooping cough.
  • Koch and Pasteur established germ theory, culture techniques and a set of postulates to follow in order to create the link between a particular pathogen and disease.
  • Vaccines to combat childhood illnesses were developed through a knowledge of germ theory.
  • The infant/childhood mortality rate has improved significantly, and hence life expectancy, due to the immunity provided by vaccines.
  • An understanding of inherited disorders has also improved lifespans with early diagnosis and prenatal genetic screening for genetic disorders and illnesses.
  • Antibiotic remedies were developed to combat bacterial diseases such as Staphylococcus aureus, due to an understanding of the difference between prokaryotic and eukaryotic cells.
  • With the use of antibiotics many diseases were then no longer life threatening, leading to improved mortality rates across all ages.
  • However, bacterial resistance has resulted with the overuse of antibiotics, so some diseases are now unresponsive to antibiotic treatment.
  • Epidemiology studies involving intricate planning and design, control groups and large scale analysis of data have lead to improvements in the treatment of non-infectious diseases such as cancer.
  • For example the discovery of links between smoking and lung cancer, sun exposure and melanoma, obesity and type II diabetes, has lead to widespread public health campaigns to inform people of the health risks and lowered the associated mortality rates.
  • Improved hygiene, food storage and preservation, and water filtration also occurred in the 20th century leading to fewer preventable diseases and hence increased life spans for all age groups.
  • Improved quarantine requirements have helped prevent the spread of plant, animal and human diseases via international travel.
  • In conclusion, developments in biology have lead to increased life expectancy across all age groups, with the biggest improvements for babies and children.
  • These benefits are not necessarily a worldwide phenomenon as poor living conditions and access to medical treatment is not available in many poor socioeconomic communities.
Show Worked Solution
  • For all ages listed in the graph, life expectancy increased during the 20th century.
  • The lifespan from birth has increased more significantly than other ages ~ 48 to 74 years.
  • The smallest increase being for 60 year olds at ~ 5 years.
  • The ability to understand pathogens and the causes of infectious disease (Koch and Pasteur) has led to early identification and treatment of childhood illnesses such as rubella, polio and whooping cough.
  • Koch and Pasteur established germ theory, culture techniques and a set of postulates to follow in order to create the link between a particular pathogen and disease.
  • Vaccines to combat childhood illnesses were developed through a knowledge of germ theory.
  • The infant/childhood mortality rate has improved significantly, and hence life expectancy, due to the immunity provided by vaccines.
  • An understanding of inherited disorders has also improved lifespans with early diagnosis and prenatal genetic screening for genetic disorders and illnesses.
  • Antibiotic remedies were developed to combat bacterial diseases such as Staphylococcus aureus, due to an understanding of the difference between prokaryotic and eukaryotic cells.
  • With the use of antibiotics many diseases were then no longer life threatening, leading to improved mortality rates across all ages.
  • However, bacterial resistance has resulted with the overuse of antibiotics, so some diseases are now unresponsive to antibiotic treatment.
  • Epidemiology studies involving intricate planning and design, control groups and large scale analysis of data have lead to improvements in the treatment of non-infectious diseases such as cancer.
  • For example the discovery of links between smoking and lung cancer, sun exposure and melanoma, obesity and type II diabetes, has lead to widespread public health campaigns to inform people of the health risks and lowered the associated mortality rates.
  • Improved hygiene, food storage and preservation, and water filtration also occurred in the 20th century leading to fewer preventable diseases and hence increased life spans for all age groups.
  • Improved quarantine requirements have helped prevent the spread of plant, animal and human diseases via international travel.
  • In conclusion, developments in biology have lead to increased life expectancy across all age groups, with the biggest improvements for babies and children.
  • These benefits are not necessarily

♦♦ Mean mark 35%.

BIOLOGY, M7 2019 HSC 33d

Alzheimer's disease causes destruction of brain tissue, dementia and eventually death.

The diagram shows the effect of Alzheimer's disease on the brain.

Amyloid beta protein is produced in the human brain throughout life. In people with Alzheimer's disease, it accumulates in excessive amounts.

The gene with the greatest known effect on the risk of developing late-onset Alzheimer's disease is called APOE. It is found on chromosome 19.

The APOE gene has multiple alleles, including e2, e3 and e4 .

The table shows the risk of developing Alzheimer's disease for various APOE genotypes compared to average risk in the population.
 

  

A large epidemiological study was conducted. It used historical data to investigate the association between Herpes simplex virus (HSV) infection and dementia. Dementia is caused by a variety of brain illnesses. Alzheimer's disease is the most common cause of dementia.

The study used the records of 8362 patients with HSV infection and 25086 randomly selected sex- and age-matched control patients without HSV infection. Some of the patients with HSV had been treated with antiviral medication.

The graph below shows some results of the study.
 

Diseases are classified as infectious or non-infectious.

Evaluate whether Alzheimer's disease should be classified as an infectious disease or a non-infectious disease. In your answer, include reference to the information and data provided above.   (8 marks)

Show Answers Only

Infectious vs non-infection disease classification

  • Infectious diseases are a result of pathogens, biological agents of disease, which transmit disease between hosts. A pathogen is a cause of a certain disease if it meets the criteria in Koch’s postulates.
  • The study above shows the association between HSV and Alzheimer’s.
  • The study is conducted over a long period and includes a large and controlled sample size, so the assumption can be made that the findings are valid.
  • HSV is an infectious disease as it is caused by a pathogen, the virus Herpes simplex.
  • The findings show that treating HSV with antiviral medication also reduces the risk of developing Alzheimer’s.
  • This may mean that Alzheimer’s is also a virus and therefore an infectious disease. 
  • Non-infectious diseases are not contagious and do not spread from person to person. They are a result of environmental factors or genetic conditions.
  • Alzheimer’s is the result of a build-up of the amyloid beta protein, which is produced in the brain.
  • The synthesis of this protein is regulated by the APOE gene. This gene also has various alleles, each of which in different combinations can increase or decrease a individual’s risk of developing Alzheimer’s.
  • This indicates that Alzheimer’s is a non-infectious disease, as it is not transmitted by a pathogen. Rather, it results from a natural build up of a specific protein, which may be accelerated or reduced based on genotype. 

Conclusion

  • From the information provided it is not possible to accurately classify Alzheimer’s as either an infectious or non-infectious disease.
  • There is evidence to support that the risk of developing Alzheimer’s can be linked to both antiviral and virus traits as well as genotype.
Show Worked Solution

Infectious vs non-infection disease classification

  • Infectious diseases are a result of pathogens, biological agents of disease, which transmit disease between hosts. A pathogen is a cause of a certain disease if it meets the criteria in Koch’s postulates.
  • The study above shows the association between HSV and Alzheimer’s.
  • The study is conducted over a long period and includes a large and controlled sample size, so the assumption can be made that the findings are valid.
  • HSV is an infectious disease as it is caused by a pathogen, the virus Herpes simplex.
  • The findings show that treating HSV with antiviral medication also reduces the risk of developing Alzheimer’s.
  • This may mean that Alzheimer’s is also a virus and therefore an infectious disease. 
  • Non-infectious diseases are not contagious and do not spread from person to person. They are a result of environmental factors or genetic conditions.
  • Alzheimer’s is the result of a build-up of the amyloid beta protein, which is produced in the brain.
  • The synthesis of this protein is regulated by the APOE gene. This gene also has various alleles, each of which in different combinations can increase or decrease a individual’s risk of developing Alzheimer’s.
  • This indicates that Alzheimer’s is a non-infectious disease, as it is not transmitted by a pathogen. Rather, it results from a natural build up of a specific protein, which may be accelerated or reduced based on genotype. 

Conclusion

  • From the information provided it is not possible to accurately classify Alzheimer’s as either an infectious or non-infectious disease.
  • There is evidence to support that the risk of developing Alzheimer’s can be linked to both antiviral and virus traits as well as genotype.

♦♦ Mean mark 46%.

BIOLOGY, M8 2022 HSC 31a

Studies have shown that lung cancer can be linked to environmental causes.

In one historical study across 29 health districts in Japan, non-smoking married women aged 40 and above were followed up for 14 years (1966-79) and annual mortality rates for lung cancer were assessed according to the smoking habits of their husbands. They were compared to women who smoked.

The results are shown.

  1. Evaluate the method used in this epidemiological study.   (4 marks)

  2. Justify conclusions that could be drawn from the results of the study.   (3 marks)

Show Answers Only

i.    Sample size:

  • Large sample (36 302 average amount per group).
  • Widespread (29 different health districts) which means results will be more accurate.

Other factors to consider:

  • The study was conducted over an extended period of 14 years, which will again lead to more accurate results.
  • The study also has a control group (non-smokers with non-smoker husbands) which provides a base for the study.
  • Overall, it can be concluded that this study is a valid way of showing the relationship between first and second hand smoking and mortality in women.

ii.   Conclusions of study:

  • The control group (non-smoker women with non-smoker husbands) shows that 8.7 women per 100 000 have died to lung cancer.
  • This could be due to friends or other family members who smoke or exposure to smoke in the workplace.
  • Other possible contributing factors in Japan, such as poor air quality can have an effect but be outside the scope of the study.
  • The study also shows that non-smoker women who have smoker husbands have almost double the mortality of women in the control group, and women who smoke themselves with smoker husbands have triple the mortality rate.
  • With this information, it can be concluded that both smoking and exposure to second hand smoke, increases a woman’s chance of death by lung cancer.
Show Worked Solution

i.    Sample size:

  • Large sample (36 302 average amount per group).
  • Widespread (29 different health districts) which means results will be more accurate.

Other factors to consider:

  • The study was conducted over an extended period of 14 years, which will again lead to more accurate results.
  • The study also has a control group (non-smokers with non-smoker husbands) which provides a base for the study.
  • Overall, it can be concluded that this study is a valid way of showing the relationship between first and second hand smoking and mortality in women.

♦ Mean mark (i) 44%.
ii.   Conclusions of study:

  • The control group (non-smoker women with non-smoker husbands) shows that 8.7 women per 100 000 have died to lung cancer.
  • This could be due to friends or other family members who smoke or exposure to smoke in the workplace.
  • Other possible contributing factors in Japan, such as poor air quality can have an effect but be outside the scope of the study.
  • The study also shows that non-smoker women who have smoker husbands have almost double the mortality of women in the control group, and women who smoke themselves with smoker husbands have triple the mortality rate.
  • With this information, it can be concluded that both smoking and exposure to second hand smoke, increases a woman’s chance of death by lung cancer.

BIOLOGY, M8 2022 HSC 5 MC

Data for incidence of notifiable infectious diseases in Australia are shown in the table.

\begin{array}{|l|c|}
\hline
\rule{0pt}{2.5ex}\textit{Disease} & \textit{Percent of all cases of infectious} \\
\textit{} & \textit{disease notified for 2019} \\
\hline
\rule{0pt}{2.5ex}\text{Influenza}\rule[-1ex]{0pt}{0pt}&\text{53}\\
\hline
\rule{0pt}{2.5ex}\text{Sexually transmitted infections}\rule[-1ex]{0pt}{0pt}& \text{25}\\
\hline
\rule{0pt}{2.5ex}\text{Gastrointestinal diseases}\rule[-1ex]{0pt}{0pt}& \text{10} \\
\hline
\rule{0pt}{2.5ex}\text{Vaccine preventable diseases}\rule[-1ex]{0pt}{0pt}& \text{9} \\
\text{excluding influenza}\rule[-1ex]{0pt}{0pt}& \text{} \\
\hline
\rule{0pt}{2.5ex}\text{Other}\rule[-1ex]{0pt}{0pt}& \text{3} \\
\hline
\end{array}

Which type of graph should be chosen to best represent these data?

  1. A column graph because percentages are continuous.
  2. A column graph because diseases are categorical.
  3. A line graph because percentages are continuous.
  4. A line graph because diseases are categorical.
Show Answers Only

`B`

Show Worked Solution
  • A column graph would be the most appropriate as the diseases are divided into categories.

`=>B`

BIOLOGY, M8 2020 HSC 27

Exposure to arsenic in drinking water has been associated with the onset of many diseases. The World Health Organisation recommends arsenic levels in drinking water should be below 10 `mu`g L-1 .

An epidemiological study involving 58 406 young adults was conducted over an 11-year period in one country to investigate young-adult mortality due to chronic exposure to arsenic in local drinking water. Each individual's average exposure and cumulative exposure to arsenic over the time of the study were calculated. Age, sex, education and socioeconomic status were taken into account during the analysis of the results.

The graphs show survival rates for males and females over the 11-year period associated with different average levels of exposure to arsenic in drinking water.
 

  1. Identify TWO features of the method used that contributed to the validity of this study.   (2 marks)

  2. The hypothesis put forward was that exposure to arsenic in drinking water increases mortality in young adults.
  3. Discuss the data presented in the graphs in relation to this hypothesis.   (4 marks)

Show Answers Only

a.   Successful answers should include two of the following:

  • The identification of the age and sex of participants
  • Socioeconomic status 
  • Arsenic exposure
  • Large sample size
  • The length of the study period

b.   Consider the less than 90 `mu`g L-1 group:

  • The survival rate for both males and females was highest in this “control” group. This is despite the group being exposed to more arsenic than recommended by WHO.
  • In both males and females, increased exposure to arsenic led to lower survival rates.
  • This gradual survival decrease is best seen in males.
  • In females, all doses over 90 `mu`g L-1 lead to similar survival decrease, suggesting other factors, such as a gene or diet, are interacting with the dosage of arsenic.
  • Over the 11 year period, survival progressively declined, supporting the hypothesis.
  • It is important to note, however, that despite the large sample size and time period the study was conducted, survival only dropped by 0.1%.
Show Worked Solution

a.   Successful answers should include two of the following:

  • The identification of the age and sex of participants
  • Socioeconomic status 
  • Arsenic exposure
  • Large sample size
  • The length of the study period

b.   Consider the less than 90 `mu`g L-1 group:

  • The survival rate for both males and females was highest in this “control” group. This is despite the group being exposed to more arsenic than recommended by WHO.
  • In both males and females, increased exposure to arsenic led to lower survival rates.
  • This gradual survival decrease is best seen in males.
  • In females, all doses over 90 `mu`g L-1 lead to similar survival decrease, suggesting other factors, such as a gene or diet, are interacting with the dosage of arsenic.
  • Over the 11 year period, survival progressively declined, supporting the hypothesis.
  • It is important to note, however, that despite the large sample size and time period the study was conducted, survival only dropped by 0.1%.

BIOLOGY, M8 2021 HSC 31

Millions of people around the world take drugs known as statins, which have been shown to reduce the incidence of heart attacks and strokes in vulnerable patients. However, up to 20% of people stop taking statins due to side-effects such as muscle aches, fatigue, feeling sick and joint pain.

A recent study at a public hospital focused on 60 patients who had all stopped taking statins in the past due to severe side-effects. Patients took statin tablets for four months, placebo tablets for four months and no tablets for four months.

Every day for the year the patients scored, from zero to 100, how bad their symptoms were. The results are shown.
 

Evaluate this study and its results.   (6 marks)

Show Answers Only
  • The data shows that when no tablets were taken, patients still displayed symptoms of the side effects (score 8.0). Taking the statin tablets doubled the severity of the side effects (score 16.3), however, placebo tablets with no active ingredients still produced similar results (score 15.4).
  • This seems to indicate that the side effects may arise as a result of other factors.
  • However, this study cannot be regarded as valid. Only 60 patients were involved in comparison to the millions that take statin tablets.
  • The results were also taken in a qualitative way and cannot be regarded as reliable.
  • The study should also have included a control group of people who have never taken statins to be used for a comparison to improve validity.
  • While the raw data provides data which is valuable and should be followed up with a large, randomised control trial, the study itself cannot be regarded as valid.
Show Worked Solution
  • The data shows that when no tablets were taken, patients still displayed symptoms of the side effects (score 8.0). Taking the statin tablets doubled the severity of the side effects (score 16.3), however, placebo tablets with no active ingredients still produced similar results (score 15.4).
  • This seems to indicate that the side effects may arise as a result of other factors.
  • However, this study cannot be regarded as valid. Only 60 patients were involved in comparison to the millions that take statin tablets.
  • The results were also taken in a qualitative way and cannot be regarded as reliable.
  • The study should also have included a control group of people who have never taken statins to be used for a comparison to improve validity.
  • While the raw data provides data which is valuable and should be followed up with a large, randomised control trial, the study itself cannot be regarded as valid.
♦♦ Mean mark 38%.