PUB HLTH 2007 - Epidemiology for Health and Medical Sciences - Nursing Assignment Help

Assignment Task

The questions in this assignment are based on a proposed study (yet to take place) that is detailed in the  following recently published paper:  
Wang H et al. The efficacy of transcranial alternating current stimulation for treating post-stroke  depression. Study Protocol Clinical Trial (SPIRIT Compliant). Medicine 2020; 99:16(e19671).  
Please note that unless otherwise stated, answers to the assignment questions are not given in the paper  but it may provide some useful background for the context, if you are interested. 
The paper reports on a proposed 8-week, double-blind, randomized, placebo-controlled trial (RCT) to  assess the efficacy of a treatment called transcranial alternating current simulation (tACS) for participants  with post-stroke depression (PSD) relative to a ‘sham’ (placebo) procedure. It is planned that participants  will be treated for four weeks (with tACS or sham procedure) and then have an additional four weeks of  follow-up – at which point, the primary outcome is determined for each patient. 
The primary outcome for this study is whether patients have an improvement at week 8 (yes/no) with  ‘improvement’ determined by objective clinical tools (see publication for further details if interested).
Background Summary 
As summarised in the Introduction of the publication by Wang H et al. (2020), post-stroke depression (PSD)  is very common, affecting approximately one third of stroke survivors at any one point in time. Different  options, in particular anti-depressants, have proven to be effective at treating PSD but their potential side  effects include nausea, diarrhea, fatigue and dizziness as well as a higher chance of hemorrhagic  complications and another stroke.  
In the search for alternatives, this study proposes to examine the efficacy of transcranial alternating  current stimulation (tACS) for PSD. While the Food and Drug Administration (FDA) have approved the use  of this treatment for major depressive disorder, side effects do include the possibility of seizures.  
Please note that while you are expected to work your way through some formulae in the assignment (and  to show your working – hand written, typed or as an Excel screen shot), there are opportunities to check  your answers later when you access the data in Stata. 
Another very important note: When answering questions that include use of Stata or Excel, don’t forget to  include your output copy and pasted (using a fixed-width font like Courier New) or as a screenshot, so that  it is readable!  
Question 1 
The Stata dataset tacs simulated trial.dta contains fictitious data which have been  simulated based on the design of this trial. The dataset contains information on 100 fake patients, of  whom 50 are randomised to the tACS (intervention) group and 50 are randomised to the Sham  procedure (control) group. The dataset contains the following variables: 
(a) Use the tab command in Stata to create a 2x2 contingency table to display the relationship  between treatment and the primary outcome improve_8wk and provide your output. [2 marks] 
(b) State the nature of the variable improve_8wk (i.e. the primary outcome stated on page 1) and  briefly explain why a Chi-square test statistic would be necessary in this study.   
(c) State the Null and Alternative Hypotheses for the primary research question of interest in this  study. [Hint: The lectures will be more helpful than the publication here.]  
(d) Calculate and report the expected values in the contingency table (to 2 decimal places), if the Null  Hypothesis is true and show your working. 
(e) We can use the information from parts (a), (b) and (c) above to calculate that the statistic for  this table to show that it is 5.09. One important part of this process is to calculate O – E for each cell  in the contingency table. Briefly explain why this difference is useful. [Hint: Think about what large  differences for O – E might tell us.]  
(f) What is the number of degrees of freedom for this test statistic? 
(g) Use the appropriate command in Stata to perform the chi-square test resulting in the test statistic  reported in bold in Q1 (e). Check that your results are consistent. Include your output and note  (using highlighting, arrows or similar) the parts of the output that identify the chi-square test  statistic and the P value.  
(h) Based on your result from (g), comment on the strength of the evidence against the Null Hypothesis  and what can subsequently be concluded about the primary research question.  [2 marks, 2-3 sentences] 
(i) When reporting results from a trial such as this, researchers may decide to state the observed  difference in proportions improving in each treatment group and/or the odds ratio. Determine the  odds ratio of improvement in the tACS group, relative to the Sham group (by hand and a calculator)  and explain what this tells us.  

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