Extracted text: O CONFIDENCE INTERVALS AND HYPO.. Confidence interval for the... A random selection of volunteers at a research institute has been exposed to a weak flu virus. After the volunteers began to have flu symptoms, 20 of them were given multivitamin tablets daily that contained i gram of vitamin C and 3 grams of various other vitamins and minerals. The remaining 20 volunteers were given tablets containing 4 grams of vitamin C only. For each individual, the length of time taken to recover from the flu was recorded. At the end of the experiment the following data were obtained. Days to recover from flu Treated with 6.4, 5.8, 7.9, 5.8, 1.8, 3.6, 10.0, 5.9, 10.0, 4.0, 6.4, 9.0, 5.7, 5.5, 8.1, 5.6, 7.8, 8.5, 5.2, 4.6 multivitamin Treated with 3.0, 2.6, 4.0, 4.7, 7.9, 2.6, 4.1, 2.5, 3.0, 2.8, 4.0, 4.5, 2.4, 5.8, 4.8, 1.7, 4.2, 2.0, 2.1, 4.1 vitamin C Send data to calculator v Send data to Excel Suppose that it is known that the population standard deviation of recovery time from the flu is 1.8 days when treated with multivitamins and that the population standard deviation of recovery time from the flu is 1.5 days when treated with vitamin C tablets. Suppose also that both populations are approximately normally distributed. Construct a 90% confidence interval for the difference µ,-4, between the mean recovery time when treated with multivitamins (µ,) and the mean recovery time when treated with vitamin C only (u,). Then find the lower limit and upper limit of the 90% confidence interval. Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal places. (If necessary, consult a list of formulas.) Lower limit: n Upper limit: I