7. Refer to Reading 3 for the following: (a) What is the difference between: (i) A prospective and a retrospective study? A prospective study begins in the present and continues into the future and watches for the development of disease or the presence of risk factors or protective factors. A retrospective study looks backwards and examines the possible risk and protection factors. (ii) A longitudinal study and a cross-sectional study? In a longitudinal study the same individuals are observed over a period of time and in a cross-sectional study data from lots of different individuals is collected at a specific point in time. (6 marks) (b) Was the study in Reading 3: (i) Prospective or retrospective? Retrospective study (ii) Longitudinal …show more content…
(2 marks) A larger number of controls was chosen to maximise the statistical power of the study. (d) In Table 2, one set of figures reads: 3.6 (0.40, 32.36; 0.27). Explain, in words, the meaning of each of these numbers. (8 marks) The measure of association between exposure and an outcome is the odds ratio which is 3.6. the 95% confidence interval of 0.40,32.36 shows the precision of the odds ratio and 0.27 is the p-value –how statistically different the cases and controls are. (e) From the set of figures in (d) above, would you say that being exposed to a spa pool was a significant factor in the Legionnaires' disease outbreak or not? How can you tell? (4 marks) Being exposed to a spa pool is a significant factor in Legionnaires disease because of the high odds ratio which is in the range of the 95% confidence interval and the low p-value. 8. Refer to Reading 6 (page 51) for the following: (a) What is meant by "highly skewed"? Also include a sketch to illustrate your answer. (2 marks) Highly skewed data is asymmetrical in the distribution of data, this can be seen in the image below which shows a normal is distribution, and data that is negatively skewed and data that is positively