Business Decision Analytics under Undertainty (33:136:400)
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:
- Users enter the site at an average interval of 1.5 seconds.
- The website then displays the survey page. This page is complicated and
requires 0.3 seconds of server time to display.
- After the display of the survey page, approximately 5% of users “give
up” and do not respond
- 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.
- 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.
- 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.
- 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:
- What is the average delay users will experience viewing the the initial
- What average delay will successful users experience between pressing the
“submit” button and seeing the complete confirmation screen?
- What average delay will users experience between submitting an invalid or
incomplete survey and seeing the redisplayed survey page with error