Medical Statistics MATH38072 – Semester 2 2023/2024
Coursework Assignment
• Submission date: Monday April 15th 2024 (10:00 BST)
• Submission method: Via Blackboard
• Your coursework submission should take the form of a single electronic file. This should
preferably be in the form of a Microsoft WORD document; if you have used Latex (or another
document preparation app) instead of WORD, or handwritten part of you solution, please
ensure that you create a single PDF document and upload that instead. Submission of multiple
files is not accepted; should you submit more than one file, only the first file submitted will be
accepted and marked.
• Any student who submits their coursework assignment after the deadline without approved
mitigating circumstances or DASS extension will be subject to the standard University
penalties.
• Please note that by making a submission you are declaring the work to be your own.
• This coursework is expected to take you approximately 4-5 hours, including reading of the
relevant parts of the trial report, assuming reasonable prior assimilation of course unit material.
Read through the clinical trial report “Rondanelli, M., Opizzi, A., Monteferrario, F., Antoniello, N.,
Manni, R. and Klersy, C. (2011), The Effect of Melatonin, Magnesium, and Zinc on Primary
Insomnia in Long-Term Care Facility Residents in Italy: A Double-Blind, Placebo-Controlled Clinical
Trial. Journal of the American Geriatrics Society; 59:82-90” and then answer the three questions
given below. The trial report manuscript can be found via the link
5415.2010.03232.x and a PDF copy is also available for download from Blackboard.
Q1.
i. Based on the material provided in the trial report manuscript, describe the randomisation
algorithm (method) used to allocate the trial participants into the two (intervention and control)
groups.
[1 mark]
ii. Briefly describe the process of performing the actual randomisation of participants once they
had been recruited.
[1 mark]
iii. What further details would you have expected to see included in the trial report manuscript
about the randomisation algorithm and randomisation process?
[2 marks]
[continued]
iv. Using your answers to parts i., ii. and iii. as appropriate, explain whether you believe that the
allocation concealment was adequate to avoid assignment bias (i.e. bias due to the process of
assigning participants to the treatment and control groups not being truly random).
[2 marks]
[TOTAL Q1: 6 marks]
Q2.
The authors’ justification for the sample size in the trial report manuscript was: “Based on evidence
in the literature44, PSQI score was expected to decrease 0.84 points in the placebo group and 3.20
(difference 2.36) in the treated group. A common standard deviation (SD) of 2.50 was considered
in the computations. A sample size of 19 participants per group has 80% power to detect such a
difference (effect size of 1 SD) with a Student t-test for independent samples and a significance
level of 5% (two-sided). To adjust for an expected drop-out rate of 10%, approximately 42
participants (21 per group) needed to be enrolled in the study.”
i. Using the sample size formula included in your course materials, calculate the required sample
size using the set of parameters: target treatment effect=2.36, standard deviation=2.50,
a=0.05, b=0.2 and attrition rate=0.1, as provided in the authors’ justification above. (Please
show all your workings.)
[3 marks]
ii. Comment on whether your calculated sample size is the same as that presented in the trial
report manuscript and provide a possible reason for any discrepancy you observe.
[2 marks]
[TOTAL Q2: 5 marks]
Q3.
i. Assuming that the Pittsburgh Sleep Quality Index (PSQI) is approximately normally
distributed and that the population variances are the same in the two groups, use the
summary statistics for the 60-day PSQI to compute a 95% confidence interval (CI) for the
treatment effect of the melatonin, magnesium and zinc food supplement (i.e. the between-
groups difference in mean PSQI at 60 days).
[3 marks]
ii. Comment on the apparent validity of the assumptions (of normality and equality of
variances) that you have made in performing the t-test in part i.
[2 marks]
[continued]
iii. The research team used the change from baseline to 60 days in the PSQI as their primary
outcome when estimating the treatment effect of the melatonin, magnesium and zinc food
supplement, and provided a point estimate of 6.8 and 95%CI of 5.4 to 8.3 in the trial report
manuscript. Briefly discuss the advantages and disadvantages of estimating the treatment
effect using the primary outcome measure of the change from baseline to 60 days in the
PSQI rather than using the 60-day PSQI.
[2 marks]
iv. If you were advising the research team on the optimal method of statistical analysis to
estimate the treatment effect, what method would you advise? (Ensure that you provide
your reasoning behind your advice.)
[2 marks]
Group n Mean Standard deviation
Treatment 22 5.5 1.9
Placebo 21 12.0 4.4
[TOTAL Q3: 9 marks]
[TOTAL 20 marks (20% contribution to Course Unit final mark)]
[End Coursework Assignment]
