Cheatography
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OIDD midterm review good luck
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Lecture 2
Flow Rate 
Min between demand and capacity 
Utilization = R/Capacity 
fraction of time spent working 
Cycle Time = 1/ Flow Rate 
Time between when units exit process 
Flow Time = I/R 
Time unit spends in process 
Cost of Direct Labor 
=(wages per unit of time x #of workers) / Flow Rate 
Labor Content 
sum of processing times involving labor (don't multiply by #of workers) 
Labor Utilization 
= R / Labor Capacity 
Labor Capacity 
= N (# of workers) / Labor content 
Takt Time =1/ Demand Rate 
Time between when flow units are demanded 
Target Manpower = Labor Content/ Takt Time 
= Labor Content/ Takt Time 
Goal of Line Balancing 
Find min cycle time 

Process Flows (Lecture 1)
Little's Law: I = R x T 
I= Inventory, R= Flow Rate, T= Flow Time 
Days of Supply = I/R = 1/Turns 
The "T" in Little's Law (add def) 
Inventory Turns = 1/T = R/I = COGS/ I 
COGS = R, the flow rate 
Gross Margin % = (Price  Cost) / Price 
Decision trees
Maximin Decision 
Find the minimums of each branch, then choose the max of the mins 
Maximax Decision 
Find the max of each branch, then choose the max of the maxes 
Expected value of Perfect info 
= (expected value of decision w/ perfect info)  (expected value of decision w/o perfect info) 
Queues
Length of queue at time T = T x (Demand  Capacity) 
Time to serve Qth person in queue = Q/Capacity 
Time to serve customer arriving at time T = T x (Demand/Capacity1) 
Avg time to serve customers in the queue = 1/2 x T x (Demand/Capacity 1) 
Variables to know 
a= inter arrival time, m= # of workers/kiosks, p = avg processing time 
Demand = 1/a 
Capacity= m x (1/p) 
Utilization = P / ( a x m) 
m = P /( a x utilization) 
Time spent in system = Time in queue + Time in processing 
Inventory = Inventory in queue + Inventory in service 
Inventory in queue = Time in queue/ a 
Inventory in service = p/a 
CVa= Standard deviation inter arrival time / avg inter arrival time 
CVp= Standard deviation processing time/ avg processing time 
Time in queue increases dramatically as utilization approaches 100% 


Yield and Capacity of Process
Yield = Flow Rate goof output/ Flow rate bad output 
Yield of Process = Product of resource yields 
Implied Utilization = Demand/ Capacity 
Can be over 100% , bottleneck has highest IU 
Capacity = 1/Processing Time 
Processing Time = 1/Capacity 
Demand (in min of work) = Processing time x Demand 
Required input = Desired output/ Process yield 
Required resource capacity = Resource's demand with required input 
Required resource capacity = Resource's demand with required input 
Finding capacity of process 
Find capacity of each step and find the bottleneck 
Solving Questions
What the question is asking 
Approach to take 
Inventory costs are what percent of purchasing costs? 
Find Flow Time. Then multiply annual inventory cost percentage by flow time in years and by individual unit cost 
Cost to hold inventory for a year 
Cost of individual unit x annual holding cost percentage 
What is the avg time... 
Find flow time 
Total time to process 20 customers 
Time to process 1st customer (sum of processing times) + time to process other customers ( 19 x Cycle Time) 
Total ordering costs 
(K x R) / Q 
Total holding costs 
1/2 x Qh 
How many individual units should they produce in each batch 
Use desired capacity to find full batch size. Then multiply batch size by ratio of individual demand/capacity over total demand/capacity 
If company ordered a specific number of cases at a time, what would be their holding and ordering costs 
Find C(Q) 
If company ordered a specific number of cases, what would be holding and ordering cost per case 
Find C(Q)/ R 
Quantity of cases per order 
Find EOQ 
How long will you wait if you are nth in line 
Find the time to serve the number of people in front of you. 


Setup Times and Batching
Capacity = Number of units produced/ Time to Produce units 
Utilization (with a setup time) = Flow rate x Processing Time 
EOQ and Quantity Discounts
Inventory Variables 
Q= quantity in each order, R=Flow Rate, h = inventory holding cost per unit time, K= fixed vost per order 
Time between shipments = Q/R 
Avg inventory = Q/2 
Number of orders placed per unit of time = R/Q 
Capacity (in min of work/hr) = #of workers x 60 
Quantity minimizing ordering and holding costs
Ordering plus inventory holding cost per unit time
