All work must be shown. Failure to do so will result in a grade of "0". a) York University students use printing companies to print their documents in which they complain about the companies being too slow. A student group conducted a study to help determine which type of printing company to choose. In the study, six documents are printed by two different printer companies. The number of seconds it took for Company A to print a document was 20.25, 24, 16, 13.5, 18, 15.75 and for the other printer, Company B, it took 19, 26.75, 12, 14, 18, 12 seconds. Can they conclude that Company A is more efficient than Company B? Use 5% significance level. b) State a condition that must be true for the above test to be valid. c) Solve Part c) independently. Pfizer has just developed a medicine for COVID to alleviate the symptoms of COVID. Still, they are concerned about the variability in the amount of time until the medicine becomes effective. In a random sample of 8 individuals who suffer from COVID, the amount of time (in hours) for the medicine to take effect was recorded. "?" represents missing data and some relevant statistics are given below. Estimate with 90% confidence the variability in the amount of time for the medicine to become effective. Amount of time (x): 12, 16, 9, ?, 8, 4, ?, 4 [x = 62, [x2 = 618, Sx = 4.4320