Size: px
Start display at page:



1 SECOND M.B. AND SECOND VETERINARY M.B. EXAMINATIONS INTRODUCTION TO THE SCIENTIFIC BASIS OF MEDICINE EXAMINATION Friday 14 March am Attempt all ten questions. For each question, choose the single best answer out of the five possible options to. Mark your chosen answer clearly on the separate answer sheet in the appropriate box. Ensure you enter your candidate number and letter on the answer sheet as instructed. Please leave all papers, including question and answer sheets and any rough working paper, in the examination hall when you leave. STATIONERY REQUIREMENTS Answer sheet You may not start to read the questions printed on the subsequent pages of this question paper until instructed that you may do so by the Invigilator

2 2 Q1. A paper is submitted to a clinical journal that describes the use of a new surgical technique on a patient and reports a successful outcome when the technique is used in the treatment of a single patient. Which of the following statements best describes the paper. This paper constitutes good evidence to adopt the new procedure. This paper is an example of qualitative research. This paper is an example of a case-control study. This paper is of no value because it describes the result from a single patient and should not be published. All new surgical procedures are first reported in a paper describing the results from the first attempt. Q2. In order to test the hypothesis that the dried food fed to cats is responsible for an increased risk of urolithiasis a study is performed examining the dietary history of a sample of 100 cats diagnosed with urolithiasis. For each case of urolithiasis two healthy cats of the same age, sex and breed were also recruited into the study to provide a comparison group and the type of food fed to these cats was recorded. 80 out of the 100 urolithiasis cats had been fed dried cat food while only 40 out of the 200 healthy cats had been fed this type of food. Which of the following statements best describes the findings of this study with regard to the hypothesis being tested? The prevalence of urolithiasis in cats is 33.3%. Healthy cats are half as likely to be fed dry cat food as compared to cats with a diagnosis of urolithiasis. The odds of a cat with urolithiasis having been fed dry cat food is 8 to 1. The risk ratio of a cat developing urolithiasis having been fed dry cat food is 4. The odds ratio of a cat with urolithiasis having been fed dry cat food as compared to a healthy cat is 16. Q3. A new serological assay has been produced to diagnose early a neoplastic condition. The test is assessed using 1000 healthy individuals and 1000 individuals for which there is already a definite diagnosis for this condition. There are 850 positive results among the individuals who have the condition and 50 positive results among the healthy individuals. 5% 15% 30% 85% 95% The specificity of the serological test for diagnosing this neoplastic condition is:

3 3 Q4. Consumption of alcohol and the smoking of tobacco products are both causal factors in the incidence of oesophageal cancer. These two risk factors are not independent, but operate synergistically. If a study was attempting to quantify the risk of smoking in the aetiology of oesophageal cancer and failed to control for the amount of alcohol consumption which of the following types of bias would influence the result? Confounding bias Design bias Recall bias Recruitment bias Selection bias Q5. In a study of an endemic infectious disease within the UK cattle population it is determined that 2% of the population are infected at any single point in time. In another study it is determined that the average duration of disease is 8 weeks. Using this information what would be your best estimate for the annual incidence of disease in a herd of 100 cows? Q6. In a study attempting to provide evidence on the outcomes following hip replacement surgery a number of data were collected. One variable that was collected was described as Cause of death within 30 days following hip replacement surgery using one of two surgical techniques in a top-ranked hospital. Which of the following best describes this type of data? Numerical, continuous Categorical, ordinal Categorical, nominal Numerical, discrete Categorical, binary

4 4 Q7. When making inferences, 95% confidence intervals are considered more informative than p-values for a variety of reasons. Which one of the statements concerning 95% confidence intervals given below is NOT true? They generally indicate whether or not a result is statistically significant at the two-sided, 0.05 level of significance. They are less open to post hoc analyses ( data-dredging ) than significance tests. They automatically include the true (population) value of the parameter being estimated. They convey the uncertainty or imprecision of an estimate. They incorporate information about the sample size involved. Q8. A one-sided p-value comparing two groups of randomly sampled data in a wellconducted study is correctly computed to be What can be inferred from this study? The study was adequately powered to detect a meaningful difference between the two groups. The null hypothesis of no difference between the population means for the two groups has a 4% chance of being true. A two-sided test on the same data is also statistically significant at 0.05 level of significance. The alternative hypothesis must be true. None of the above. Q9. Which of the following is a valid reason for a leading journal s statistical reviewer to recommend rejection of a submitted article describing a randomised controlled trial? Authors failed to consult a statistician at the correct design stage of the study. The study was not blinded (those assessing the health outcomes were aware of treatment group allocation). The abstract failed to mention a 95% confidence interval for the study s primary outcome (the main result). The study was of adequate size but the primary outcome was not statistically significant. The randomisation was done in a manner that allowed the researchers to know each patient s treatment in advance of allocation.

5 5 Q10. Mesothelioma is incurable, with a median mortality of only eight months after discovery as quoted by Stephen Jay Gould in an article entitled The median isn t the message. Which one of the following comments about newlydiagnosed mesothelioma patients is false? Their mean survival time is greater than the median due to the skewed nature of survival time distribution. They may die from a cancer different from mesothelioma. Half will live for at least 8 months. Fewer than 75% will have died within 8 months. None will live for twenty years post-diagnosis. [END OF PAPER]