XPD129 Data Handling and Staistics 1 8. XPD129 D () The 95% confidence interval of the difference in proportion of post-operative infection whether their surgeon was Lister or the other surgeon is (0.111, 0.431) comment if the difference between the success of sterilising or not sterilising Surgical instruments in preventing infections is statistically significant. [2 marks) (e) Based on this survey can you say that to a person needing an operation that sterilising surgical instruments will reduce their chances of infection? Give a reason for your answer. [2 marks]XPD129 Data Handling and Staistics 1 - 7 - 4. Joseph Lister introduced the idea of sterilising his surgical instruments when per- forming operations. Another surgeon used the old method and did not sterilise his instruments. A table showing whether the patient suffered post-operative infection is below. Other Surgeon Joseph Lister Not Infected 27 73 Infected 23 17 (a) Which is the response variable and which is the explanatory variable? [1 marks] (b) Calculate the proportion of patients for whom surgery by the other surgeon ended in infection. [1 marks] (c) Calculate the proportion of patients for whom surgery by Lister ended in in- [1 marks ] fection. Continued ...5. The average number of spelling mistakes on a student essay is 7 per page. (a) What is the expected rate of spelling mistakes? [1 marks] (b) Suggest an EXCEL command or a mathematical formula you could use to cal- culate the probability that there is at least one spelling mistake on a page of a student's essay? [4 marks] alternative hypo