DSCI-Exam 3

-Candy Incorporated stocks bubble gum game cards, an item that has a normally distributed demand during the reorder period with a mean of 12 dozen boxes and a standard deviation of 2 dozen boxes. If it is desirable to experience a stock out only 10 percent of the time, what is the appropriate safety stock? -T/F Slack is the time an activity can be delayed without impacting the completion time of the project.

- 1.7 - T

-Consider the following linear programming problem: Maximize 4X + 10Y Subject to: 3X + 4Y ≤ 480 4X + 2Y ≤ 360 all variables ≥ 0 The feasible corner points are (48,84), (0,120), (0,0), (90,0). What is the maximum possible value for the objective function? -T/F The set of solution points that satisfies all of a linear programming problem's constraints simultaneously is defined as the feasible region in graphical linear programming.

- 1200 - T

-Infeasibility means that the number of solutions to the linear programming models that satisfies all the problem's constraints is -Which of the following factors is (are) not included in ordering cost? +bill paying +obsolescence +purchasing department overhead costs +inspecting incoming inventory +developing and sending purchase orders

-0 -obsolescence

-At an automatic car wash, cars arrive randomly at a rate of 7 cars every 30 minutes. The car wash takes exactly 4 minutes. On average, what would the length of the line be? -A suburban specialty restaurant has developed a single drive-thru window. Customers order, pay, and pick up their food at the same window. Arrivals follow a Poisson distribution while service times follow an exponential distribution. If the average number of arrivals is 6 per hour and the service rate is 2 every 15 minutes, what proportion of the time is the server busy (utilized)?

-1/(7-7.5)=-2 28 minutes -3/4

At a local fast food joint, cars arrive randomly at a rate of 12 every 30 minutes. Service times are random (exponential) and average 2 minutes per arrival. The average time in the queue for each arrival is

-12/[15(15-12)]=0.267 minutes

-Given an activity's optimistic, most likely, and pessimistic time estimates of 4, 14, and 18 days respectively, compute the PERT expected activity time for this activity. -Consider a project that has an expected completion time of 30 weeks and a standard deviation of 6 weeks. What is the probability that the project will be take more than 42 weeks? (Round answer)

-13 -2.28%

-Daily demand for newspapers for the last 10 days has been as follows (listed from oldest to newest): 12, 13, 16, 15, 12, 18, 14, 12, 13, 15. Forecast sales for the next day (i.e. day 11) using a two-day moving average. -Calculate MAD for the following forecast versus actual sales figures. Forecast Actual 100 95 110 108 120 123 130 130

-14 - 12.5-10=2.5

-The annual demand of a certain item is 5400 units and the computed EOQ is 900 units. How many orders do they have to make per year? -The annual demand for a product has been projected at 2,000 units. This demand is assumed to be constant throughout the year. The ordering cost is $20 per order, and the holding cost is 20 percent of the purchase cost. Currently, the purchase cost is $40 per unit. There are 250 working days per year. Whenever an order is placed, it is known that the entire order will arrive on a truck in 6 days. How many units should the company order each time an order is placed if the company wishes to minimize total inventory cost?

-6 (5400/900) -(2*2000*20)/8=10,000 Q=100 100/2=50

-Which of the following is a general rule for crashing activities? +Crash only non-critical activities +Crash activities with zero slack. +Crash activities with the greatest number of predecessors. +Crash the path with the fewest activities. - T/F The variance of the project completion time is equal to the sum of the variances of all the activities.

-Crash activities with zero slack -F

-T/F An M│M│3 model has Poisson arrivals, exponential service times, and two channels. -The term queue discipline describes the +degree to which members of the queue renege. +sequence in which members of the queue arrived. +degree to which members of the queue are orderly and quiet. +sequence in which members of the queue are serviced. +all of the above

-F -sequence in which members of the queue are serviced

The critical path of a network is the - T/F On a practical note-if we are using waiting line analysis to study cars passing through a single tollbooth, reneging is probably not an issue.

-Longest path through the network -T

3 project phase:

-Planning phase: setting of goal or objective -Scheduling phase: assigns resources to specific activities and ties the activities together into a project network. -Project controlling occurs: monitored resources, costs, quality and budgets.

A constraint that does not affect the feasible region is a

-Redundant constraint

-T/F EVPI (Expected Value of Perfect Information) is a measure of the maximum value of additional information. -Which of the following statements is true about r2?

-T -It is also called the coefficient of determination

- T/F One difficulty in waiting line analysis is that it is sometimes difficult to place a value on customer waiting time. - T/F When looking at the arrivals at the ticket counter of a movie theater, we can assume an unlimited queue.

-T -T

Describe the basic queuing system charateristic.

-arrival characteristics. -waiting line characteristic. -service facility characteristics

Analyze a variety of operating characteristics of waiting lines.

-determining the best level of service for an organization -analyzing the trade off between cost of providing service and cost of waiting time -service level that minimize the total expected cost.

PERT CPM

-program evaluation and review technique -critical path method

4 questions of project management:

-when it should be done, -how much (and if) it has slipped from the original schedule, -what the bottlenecks are, and -what you might drop to save some time.

At a local fast-food joint, cars arrive randomly at a rate of 3 every 30 minutes. The fast food joint takes an average of 4 minutes to serve each arrival. The utilization factor for this system is:

0.4

A new shopping mall is considering setting up an information desk manned by one employee. Based upon information obtained from similar information desks, it is believed that people will arrive at the desk at the rate of 15 per hour. It takes an average of two minutes to answer a question. It is assumed that arrivals are Poisson and answer times are exponentially distributed.(be consistent with rates!)Find the probability that the employee is idle.

0.5

8 Question answered by PERT:

1.When will the entire project be completed? 2.What are the critical activities or tasks in the project that will delay the entire project if they are late? 3.Which are the non-critical activities that can run late without delaying the entire project's completion? 4.What is the probability that the project will be completed by a specific date? 5. Is the project on schedule, behind schedule, or ahead of schedule? 6. Is the money spent equal to, less than, or greater than the budgeted amount? 7.Are there enough resources available to finish the project on time? 8.If the project is to be finished in a shorter amount of time, what is the best way to accomplish this at the least cost?

A suburban specialty restaurant has developed a single drive-thru window. Customers order, pay, and pick up their food at the same window. Arrivals follow a Poisson distribution, while service times follow an exponential distribution. If the average number of arrivals is 6 per hour and the service rate is 2 every 15 minutes, what is the average number of customers in the system?

3

Consider a project that has an expected completion time of 60 weeks and a standard deviation of five weeks. What is the probability that the project will take anywhere between 60 and 65 weeks to complete? (Round to two decimals.)

34.13%

At an automatic car wash, cars arrive randomly at a rate of 7 cars every 30 minutes. The car wash takes exactly 4 minutes. On average, what would the length of the line be?

6.53

T/F CPM was developed for use in managing projects about which we have good information about activity or task completion times. T/F If we are studying the arrival of automobiles at a highway toll station, we can assume an infinite calling population.

T T

Describe the trade-off curves for cost-of-waiting time and cost-of-service.

The cost of waiting time is like the demand curve and the cost of service is like a supply curve

For an activity with more than one immediate successor activity, its latest-finish time is equal to the

smallest latest-start time among its immediate successors.

Understand the three parts of a queuing system:

the calling population the queue itself the service facility.

The crash time of an activity represents

the shortened activity time