MED5366 Stats 2 – Exam 2020-2021
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MED5366 Stats 2 – Exam 2020-2021
1)
a) Why is it better to use adjusted R2 compared to R2 for model selection in multiple regression?
[2 marks; 60 words ]
b) Why is the predicted R2 (“R-sq(pred)” in Minitab) also important when assessing multiple regression models?
[2 marks; 60 words ]
2)
a) Define the term numbers needed to treat (NNT)?
[1 mark; 30 words ]
b) What are numbers needed to treat called when they take a negative value?
[1 mark; 20 words ]
c) Why does care need to be taken when interpreting the confidence interval for the numbers needed to treat, when there is no statistically significant difference between the new and existing treatments?
[3 marks; 80 words ]
3)
a) What is the main assumption of the Wilcoxon Signed Ranks Test (other than that the data are an independent random sample and can be uniquely ranked)?
[1 mark; 20 words ]
b) Why does this assumption limit the utility of the Wilcoxon Signed Ranks
Test?
[3 marks; 80 words ]
c) If the data are not suitable for analysis with either a one-sample t-test or Wilcoxon Signed Ranks Test, what alternative test can be used? What is the limitation of this alternative test?
[2 marks; 20 words ]
2022-05-09