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Question 11ptsQuestions 1 to 7 relate to the following information.

Myopia (nearsightedness) is an eye condition that is often detected in children during their school years. Some studies have suggested that the amountand type of visual activity that a child performs (e.g., reading, TV watching, computer or video game playing, and sports/outdoor activity) may be related to the development of myopia.

The Orinda Longitudinal Study of Myopia (OLSM) was a cohort study of ocular component development and risk factors for the onset of myopia in children. Data collection began in the 19891990 school year.

The dataset contains data on children who had at least ve years of followup and were not myopic when they entered the study. All data are from their initial exam. In addition to the ocular data there is information on age at entry, year of entry, family history of myopia and hours of various visual activities. The ocular data come from a subjects right eye. A subject was coded as myopic if they became myopic at any time during the rst ve years of followup.

This dataset was described and provided by:

Hosmer, D.W., Lemeshow, S. and Sturdivant, R.X. (2013) Applied Logistic Regression, 3rd ed., New York: Wiley

The dataseta1_myopia.dtacontains the following variables:

Variable Description

id Subject identifier

studyyearYear subject entered the study

myopic Myopia within the first five years (0=No, 1=Yes)

age Age in years at first visit

gender Gender (0=Male, 1=Female)

spheqSpherical Equivalent Refraction (diopter)

al Axial length (mm)

acdAnterior Chamber Depth (mm)

ltLens Thickness (mm)

vcdVitreous Chamber Depth (mm)

sporthrHow many hours per week outside of school the child spent engaging in sports/outdoor activities

readhrHow many hours per week outside of school the child spent reading for pleasure

comphrHow many hours per week outside of school the child spent playing video/computer games or working on the computer

studyhrHow many hours per week outside of school the child spent reading or studying for school assignments

tvhrHow many hours per week outside of school the child spent watching television

diopterhrComposite of near-work activities

mommy Was the subject's mother myopic? (0=No, 1=Yes)

dadmyWas the subject's father myopic? (0=No, 1=Yes)

How many observations (children) are there in the dataset?

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Question 21ptsWhich data types best describe the following variaspheq(Spherical Equivalent Refraction)

myopic(Myopia within five years)

diopterhr(Hours per week on near-work activities)

studyyear(Year)

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Question 31ptsWhat proportion of male and female children weremyopicwithin five years of enrolling in the stu

Male: 51%, Female: 49%

Male: 87%, Female 13%

Male: 11%, Female: 15%

Male: 43%, Female, 57%

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Question 41ptsCreate a graph suitable for comparing the distribution of TV Hours per week (tvhr) for children with myopia and children without myopia.

Note:attach the graph as animagefile type such as .png, .jpg, .gifor as a .pdf. DoNOTattach a Statagraph file type .gph.

Upload

Choose a file

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Question 53ptsCompare the distributions of TV hours per week for children with myopia and without myopia.Use your graph from Question 4 and refer to appropriate descriptive statistics in your answer.

Does this suggest a difference in TV hours between children with myopia and children without myopia?

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Question 61ptsCreate a new variable calledgroupthat contains how many of the child's parents had myopia:

0: no parents with myopia (neither mother or father)

1: one parent with myopia (mother or father but not both)

2: two parents with myopia (mother and father had myopia)

What proportion of children in the study hadat least oneparent who had myopia?

25%

26%

50%

75%

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Question 72ptsEvidence suggests that myopia is highly heritable:

2020 Tedja M.S. et al, The Genetics of Myopia. In: Ang M., Wong T. (eds) Updates on Myopia. Springer, Singapore.

This means that children are more likely to be myopic if one or more of their parents is myopic. Use the variable you created in Question 6 to determine whetherthe rates of myopia in this dataset suggest a genetic relationship.

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Question 81ptsThe following picture shows two normal distributions.What can we say about their means and standard deviations?

They have thesamemean and thesamestandard deviation.

They have thesamemean anddifferentstandard deviations.

They havedifferentmeans and thesamestandard deviation.

They havedifferentmeans anddifferentstandard deviations.

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Question 91ptsThe PEFR (peak expiratory flow rate) values of a group of 11-year-old girls follow a normal distribution with mean 300 litres/min and a standard deviation of 20 litres/min.

Approximately what percentage of girls would have PEFR below 280 litres/min?

16%

68%

34%

95%

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Question 101ptsThe Bajau are an ethnic group of people from Indonesia, the Philippines and Malaysia who have lived at sea for thousands of years and have developed an extraordinary ability for breath-hold diving. In the article below, the researchers are looking for evidence that the Bajau "have larger spleens than their close geographic neighbors, the Saluan, who interact minimally with the marine environment".

Ilardo, Melissa A. et al. Physiological and Genetic Adaptations to Diving in Sea Nomads, Cell , 2013 Volume 173, Issue 3, 569 - 580.e15

Boxplots of spleen size for the Bajau and the Saluan samples are shown in Figure A below.

Compare the distribution of spleen size for Bajau and Saluan. Which of the following is the best description of this comparison?

The boxplot suggests that themedianspleen size islargerfor Bajau compared to Saluan.

The boxplot suggests that themeanspleen size issmallerfor Bajau compared to Saluan.

The boxplot suggests that theminimumspleen size islargerfor Bajau compared to Saluan.

The boxplot suggests that thevarianceof spleen size issmallerfor Bajau compared to Saluan.

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Question 111pts

Questions 11 to 12 relate to the following information.

One of the first documented randomised placebo-controlled trials was the1926 trial ofSanocrysin, a gold compound with antirheumaticeffect used to treat pulmonary tuberculosis.

J. Burns Amberson et al.,A Clinical Trial of Sanocrysin in Pulmonary Tuberculosis,American Review of Tuberculosis, 24(4), pp. 401435.

The data from the study are summarised in the table below.

SanocrysinDistilled water

Died 4 14

Alive 51 38

What proportion of patients died in theSanocrysinand distilled water groups

Sanocrysin7.3%, distilled water 26.9%

Sanocrysin7.8%, distilled water 36.8%

Sanocrysin22.2%, distilled water 77.7%

Sanocrysin26.9%, distilled water 73.1%

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Question 121ptsCalculate a 95%Confidence Interval for the difference in death rates between the distilled water group and theSanocrysingroup.

5.8% to 33.5%

12.0% to 46.0%

14.9% to 39.0%

There's not enough information

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Question 131ptsBasal blood pressure was measured for 558 older people with diagnosed or suspected coronary heart disease. The histograms of the blood pressure measurements for males and females are shown below.

Which is the best description of the Male distribution of blood pressure?

Normal

Bimodal

Extremely left-skewed

Slightly right-skewed

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Question 141ptsInfants born with low birth weight (<2500g) are at higher risk of infant mortality and birth defects. Risk factors such as maternal smoking and extreme maternal age (<16 or >40) are known to be associated with low infant birth weight.

https://www.aihw.gov.au/reports/children-youth/australias-children/contents/health/birthweightLinks to an external site.Data were collected on 189 infants and their mothers to examine whether other factors such as maternal age, maternal weight, and the number of physician visits in the first trimester were associated with low infant birth weight.

The scatterplot below shows the distribution of infant birth weight versus maternal age.

Does the scatterplot suggest a relationship between maternal age and infant birth weight?

There is evidence of apositiverelationship between maternal age and infant birth weight (birth weight increases as age increases).

There is evidence of anegativerelationship between maternal age and infant birth weight (birth weight decreases as age increases).

There isno evidenceof a relationship between maternal age and infant birth weight (no pattern in scatterplot)

There is evidence of anegativerelationship between maternal age and infant birth weight, but only for extreme maternal age (curved pattern in scatterplot).

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Question 151ptsIs a 99% confidence interval wider or narrower than a 95% confidence interval? (Assuming that the sample size, mean, and standard deviation are the same for both.)

Hint:you can explore this in Stata using the "level()" option of the cii command.

A 99% confidence interval iswiderthan a corresponding 95% confidence interval because we are more certain to have captured the true population mean.

A 99% confidence interval iswiderthan a corresponding 95% confidence interval because a larger standard deviation is used.

A 99% confidence interval isnarrowerthan a corresponding 95% confidence interval because a greater precision is used.

A 99% confidence interval isnarrowerthan a corresponding 95% confidence interval because a larger sample size is used.

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Question 161ptsQuestion 16 to 17 relate to the following information.

The first peer-reviewed research from Phase III trials on the safety and efficacy of the "Oxford" Vaccine for Covid-19 was published in January 2021.

Voysey, M. et al, Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK, The Lancet 397(10269), 99--111.https://doi.org/10.1016/S0140-6736(20)32661-1Links to an external site.The data from four trials was combined in this interim analysis. All trials involved participants being randomly assigned to receive the Oxford Vaccine (ChAdOx1 nCov-19) or a control vaccine (MenACWY). All participants received two doses (the first dose was either low or standard and the second was a standard dose for all participants). The primary efficacy outcome was based on confirmed cases of symptomatic Covid-19 (virologically verified) more than 14 days after the second dose.

The data are shown below.

Oxford Vaccine (ChAdOx1 nCov-19) Control (MenACWY)

Confirmed Covid-19 cases 30 101

Number vaccinated n=5807 n=5829

Vaccine efficacy is calculated as:

What is the vaccine efficacy for this data?

30%

62%

68%

70%

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Question 171ptsTable 1 below is the baseline characteristics table for the Oxford vaccine Phase III trials.

Is there a problem with group imbalance at baseline?

No. In these trials the groups were randomised and so any imbalance is the result of random chance.

No. The trials were all about the sample size.

Yes. The researchers should have included p-values to test for baseline imbalances.

Yes. The researchers should have used propensity score matching to fix baseline imbalances.