Decision Analysis

Question 1

Making up your mind:

Answer 1

Question 2

What are 3 good situations to use decision analysis?

Answer 2

1. there are competing treatment options with risks and benefits
2. there is important information missing (consequences, probability of failure), which can help indicate critical information gaps
3. risk occurs at different time points and the impact needs to be communicated to the owner

Question 3

What are 2 disadvantages to using decision analysis?

Answer 3

1. time-consuming and laborious
2. cannot be performed in the absence of evidence (identifying gaps of knowledge)

Question 4

What is decision analysis?

Answer 4

explicit and quantitative analysis of the cost and benefit associated to available decisions under conditions of uncertainty

Question 5

What are the 4 major steps to decision analysis?

Answer 5

1. build a decision tree (flow diagram with all possible scenarios)
2. add probabilities of occurrence for each random event
3. add cost/value (moral, emotional, economical) of each outcome
4. compare the expected cost/value of each decision (want the highest value and lowest cost)

Question 6

What 3 nodes are found on a decision tree?

Answer 6

1. DECISION NODE = conscious decision between 2 or more options (intervention type), commonly represented as a square
2. PROBABILITY (chance) NODE = outcome between 2 or more random events due to change after a decision has been made, where each outcome is associated with a probability and add up to 1 (100%), commonly represented as a circle
3. TERMINAL NODE = end of the scenario (tree branch) and is associated with an expected cost/value that combines probability and cost/value, commonly represented as a triangle

Question 7

Make a decision tree for the following scenario:

• Treatment A costs $40 and has an 80% chance of recovery
• Treatment B costs $30 and has a 60% chance of recovery
• Treatment C costs $20 and has a 40% chance of recovery
• Failure of any of these treatments leads to an additional $100 follow-up treatment

Answer 7

Question 8

When is value commonly used over cost for determining decisions?

Answer 8

production animals —> alive animals typically have more value than dead animals because they can actively produce product (dead animals still have value and are sent to abattoirs!)

Question 9

Make a decision tree for the following scenario:

• Live cows have a value of $2,250 and dead cows sent to abattoirs have a value of $500
• Left displaced abomasum has 3 possible treatment options: omentoplexy, toggle sutures, and rolling, where failure in the first 2 leads to culling and failure in rolling can either be treated with toggling or culling
• Omentoplexy = $300 with 95% chance of success
• Toggling = $150 with 88% chance of success
• Rolling = $100 with 10% chance of success

Answer 9

Question 10

What are the 4 steps of clinical decision analysis using decision trees?

Answer 10

1. design a decision tree
2. search and gather information
3. calculate cumulative probabilities
4. conduct sensitivity analyses

Question 11

What are sensitivity analyses?

Answer 11

change probabilities and costs/values on a decision tree based on individual skill or new knowledge to see how your decision may change

• better at toggling over omentoplexy = higher chance of success for toggling over the surgery
• cost of a production animal may be different than originally assumed

Question 12

Orchidectomy for cryptorchid puppies:

Answer 12