Business Decision Analytics under Undertainty (33:136:400) 
Professor Eckstein
Simulating a Simple Survey Website


You are setting up a web site to administer a large marketing survey, and are trying to decide whether to use one or two servers to operate the site. The flow of work through the website is as follows:

  1. Users enter the site at an average interval of 1.5 seconds.
  2. The website then displays the survey page. This page is complicated and requires 0.3 seconds of server time to display.
  3. After the display of the survey page, approximately 5% of users “give up” and do not respond
  4. The remaining users fill in the survey information in their local browsers (which puts no load on the server). This process can take between 10 and 300 seconds, with a typical time of 60 seconds. At the end of this process, the users press the “submit” button on their survey.
  5. The server must then check that the form is complete and the entered data are valid. This process takes 0.4 seconds of server time.
  6. When the survey contains invalid or incomplete data, which happens about 20% of the time, the user is redirected to the survey page (which is redisplayed along with some error messages). These users are effectively returned to step 2 of the process.
  7. For those who have successfully completed the survey, the system saves their information in a database and displays a confirmation page. This process requires 0.4 seconds of server time.

Based on a 5-hour simulation with a 10-minute “warmup” period, answer the following questions: with either one or two servers: