Based on the result in (a), the researcher then wanted to construct a confidence interval for the difference in the mean hours (cure of diseases) between vaccine A and vaccine B. b) State the formula you would use to construct a 95% confidence interval. Include the value of a and degrees of freedom that you will use to find the critical value in the formula. (1 mark) c) Explain why you would use the formula in (b). (1 mark) d) Compute the value of standard error mean used in the formula in (b). (2 marks) e)The 95% confidence interval for the difference in mean hours of cure between the use of vaccine A and vaccine B was between -23.5 and 103.5. What conclusion can you make on the effectiveness of the two vaccines? Justify your answer. (2 marks)Vaccine N Mean Standard Deviation A 25 477 119.383 B 25 437 103.362 A medical researcher is interested in studying the effectiveness of 2 types of vaccines to treat diseases caused by the new coronavirus. Twenty-five samples were taken to measure the cure of the diseases (in hours) after the vaccine injections were administered. The statistics are as given in the above table. Assume the two populations are normally distributed. a) Construct a 95% confidence interval for the ratio of population variances for vaccine A and vaccine B. Can we conclude whether the population variances for vaccine A and vaccine B are different? Explain why. (6 marks)