2. An account on Server A is more expensive than an account on Server B. However, Server A is faster. To see if it is optimal to go with the faster but more expensive server, a manager needs to know how faster it is. A certain computer algorithm is executed 15 times on Server A and 10 times on Server B with the following results: Server A Server B Mean 6.7 mins 7.5 rnins Standard Deviation 0.6 mins 1.2 rnins Construct a 95% condence interval for the difference between the mean execution times on Server A and Server B 3. Twenty users were asked to add a contact to a customer relationship management software (CHM) application. Eleven users completed the task on the existing version and nine different users completed the same task on the new enhanced version. The sample means are 37 and 28 seconds, respectively. The sample standard deviations are 22.4 and 13.4 seconds, respectively. Find a 99% condence interval for the difference in the average time for adding a contact between the existing version and new enhanced version. 4. Two website designs were tested on a website to see which would convert more users to register for a webinar. Out of 110 users of Design A, 15 registered for the webinar. Out of 90' Design B users, 8 registered for the webinar. Find the 90% condence interval for the difference in the conversion proportion between the two designs