University of Chicago
Booth School of Business
John Birge
ASSIGNMENT
Concept Check #1
1. (Capacity analysis.) Each circle below represents a single server, and the time indicated
represents the service time for a single job. Compute the capacity (in jobs per minute) and
cycle time (in minutes) for each of the following process flows. Assume no queues form in
front of servers, the service time for each job is exactly as indicates (i.e. deterministic), and
throughput equals capacity.
a. [1 point]
3 min
b. [1]
3 min
2 min
2 min
2 min
c. [1]
d. [1]
3 min
OR
2 min
e. [1]
3 min
AND
2 min
2. [5] (Little’s Law.) Read the article “McD’s Service Stalls at Drive-Thru” (on Canvas), which
appeared on the front page of Crain’s Chicago Business on January 2, 2006. According to QSR
magazine, the original data source, the “average time in seconds” reported in the figure “was
determined based on how long it took from when the vehicle stopped at the speaker to when the
entire order was received.” So, it does not include the waiting time before arriving at the
speaker.
The figure entitled “Time is Money”, which does the financial analysis, has serious flaws in the
operational part of the analysis. What’s wrong? Use your own personal experience of how the
drive-thru at McDonald’s operates.
3. [4] (Basic concepts in probability.) The demand for JJ Jackson’s Navy coat is a normally
distributed random variable with mean 800 and standard deviation 236.64.
Hint: You may want to take a look at the “Basic Concepts in Probability” document. (See
Session 1 readings on Canvas)
a. [2] What is the probability that the demand is less than 800?
b. [2] The probability than demand is less than x is 0.814. What is x?