# Answer all questions. Please show your working for calculations. Formatting your assignment:This format locks the information and is particularly important if you are using a Mac computer to preserve the formatting;

#### Answer all questions. Please show your working for calculations. Formatting your assignment:This format locks the information and is particularly important if you are using a Mac computer to preserve the formatting;

– Please submit your assignment online as one document in PDF format. This format locks the information and is particularly important if you are using a Mac computer to preserve the formatting;

– Use 11 point or 12 point font and 1.5 times spacing (not double spacing);

Question 1:

We will be conducting a meta-analysis to investigate whether surgery (cystectomy) combined with radiotherapy has a survival benefit (measured at 3-years) compared to radiotherapy alone for patients with bladder cancer.

a) Conduct a keyword search in (ovid) Medline (untick “Map Term to Subject Heading”) using the following search terms:

Combine these with an ‘and’ command. Present your search results in a table showing the number of studies found at each step.

b) Your search above should have found one study only. Extract the data from this study to be included in the meta-analysis. Hint: we want to look at 3 year survival comparing the two arms of the trial.

c) There were two other studies found that investigate three year survival, their results are shown in the following table:

Table1: Extracted data from two studies found via other searches

3 year survival

Cystectomy Survived

Total

Miller 1977

18

35

7                 32

Sell 1991

39

88

31               95

Calculate the study specific odds ratios comparing survival for cystectomy with survival for radiotherapy. Then calculate the Mantel-Haenszel pooled odds ratio.

d) Further analysis finds an I-squared =0.0%. Is your analysis in part c) appropriate?

e) Interpret your pooled odds ratio from part c). A test was conducted to see if the pooled odds ratio is significantly different from 1 and this test has a p-value = 0.0011, use this information to help with your interpretation.

Question 2:

The following is an extract from a paper that used directed acyclic graphs. Read the extract and then answer the questions below.

Abstract Background

In sub-Saharan Africa, malnutrition is associated with mortality in adults hospitalized for medical illness. However, it remains unclear whether this association is causal, and if causal, what the potential mediators are. We assessed whether malnutrition is causally related to mortality among hospitalized adults, and whether severe sepsis plays a mediating role.

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