ACCA Applied Skills · Performance Management

Dealing with Risk and Uncertainty in Decision-Making for ACCA PM

Risk means you can attach probabilities to outcomes; uncertainty means you cannot. For risk, calculate expected values and pick the highest profit or lowest cost. For uncertainty, apply decision rules such as maximin, maximax and minimax regret, and test key variables with sensitivity analysis.

What this chapter covers

This chapter in Performance Management teaches you how to make a decision when the future is not known. Costs, demand and selling prices rarely turn out exactly as forecast. The chapter gives you tools to handle that: expected values, decision rules, sensitivity analysis, the value of information, decision trees and simulation.

You start by separating risk from uncertainty. That split tells you which tool to use. Where probabilities exist, you use expected values and can price information. Where they do not, you use rules that reflect the decision maker's attitude: pessimistic, optimistic or regret-averse.

The chapter links to the rest of the paper. Relevant costing, CVP analysis, limiting factors, pricing and investment-type decisions all rest on forecasts. Here you ask how wrong those forecasts could be and what you would do about it. It also gives you a ready set of discussion points for written Section C answers.

Risk and uncertainty can appear in Section A, in the Section B objective test cases and in the 20-mark constructed response questions. The calculations are short and mechanical, so they are a reliable source of marks once practised. Objective test questions are marked all or nothing, so one slip in a payoff table costs the full two marks. The written points, such as limits of expected values and why simulation helps, are also easy to gain if you have a prepared list.

Dealing with risk and uncertainty in decision-making: topics in the order to study them

1Risk vs Uncertainty in Decision-MakingYou need the definitions first, because they tell you whether probabilities are available and so which technique applies.
2Expected Values and Their LimitationsThis is the core risk technique, and the later topics on information and trees build directly on it.
3Decision Rules: Maximin, Maximax and Minimax RegretThese are the tools for uncertainty, and they use the same payoff table layout you have just practised.
4Sensitivity AnalysisIt is a different kind of tool: it tests how far one variable can change before the decision changes, with no probabilities needed.
5Value of Perfect and Imperfect InformationIt compares expected values with and without information, so you must be fluent with expected values first.
6Decision Trees and SimulationTrees combine expected values, sequential choices and information, so they come last; simulation is covered alongside as a way to model many variables.

How to prepare Dealing with risk and uncertainty in decision-making

Aim for fast, accurate calculations and a short bank of written points. Practise on paper, then under timed conditions.

Write the definitions of risk and uncertainty in your own words, and list which technique goes with each.
Practise building payoff tables from a scenario. Check every cell before applying any rule.
Do expected value questions until you can finish one in about two minutes, and learn three limitations you can quote.
For maximin, maximax and minimax regret, work one table through all three rules. For regret, subtract each payoff from the best payoff in its column (the best outcome for that state of the world).
Practise sensitivity analysis as: change needed ÷ value of the variable, expressed as a percentage. Then say which variable is most critical.
Calculate the value of perfect information as expected value with perfect information minus expected value without it. Then draw decision trees from right to left, folding back from the outcomes.
Finish with timed mixed questions and write short Section C style answers that give a calculation plus a comment on its limits.

Common mistakes in Dealing with risk and uncertainty in decision-making

Using expected values when no probabilities are given, or using maximin when probabilities are given.
Fix: Read the scenario first. If it gives probabilities, think expected values. If it does not, think decision rules.
Calculating minimax regret from the wrong direction.
Fix: Regret is measured within each state of the world: best outcome in that column minus each option's outcome. For costs, the best is the lowest. Then take the maximum regret per option and pick the smallest.
Treating the expected value as the outcome that will actually happen.
Fix: Describe it as a long-run average. In written answers, note that for a one-off decision it may never occur.
Getting the value of perfect information wrong by forgetting to subtract the expected value without information.
Fix: Always finish with the difference: EV with perfect information minus the best EV without it.
Folding back a decision tree from left to right.
Fix: Start at the right-hand end, calculate expected values at chance nodes, choose the best option at decision nodes, and move left.
Giving only numbers in a written question.
Fix: Add a sentence or two on what the result means, its limitations and any further information the decision maker should seek.

Last-day revision: Dealing with risk and uncertainty in decision-making

Risk: outcomes and probabilities are known or estimable. Uncertainty: probabilities cannot be assigned.
Expected value = Σ (probability × outcome).
Expected value suits repeated decisions best; for a one-off decision the average outcome may never actually occur.
Expected value ignores the spread of outcomes and the decision maker's attitude to risk.
Maximin picks the option with the best of the worst outcomes (pessimist).
Maximax picks the option with the best of the best outcomes (optimist).
Minimax regret picks the option with the smallest of the maximum regrets. Regret = best outcome for that state minus the outcome you got.
Sensitivity = change needed for the decision to switch ÷ value of the variable, as a percentage. The smaller the percentage, the more sensitive the variable.
Sensitivity analysis changes one variable at a time and gives no probabilities.
Value of perfect information = EV with perfect information − EV without it. It is the most you should pay for information.
Imperfect information is worth less than perfect information, so its value cannot exceed that of perfect information.
Decision trees: squares are decisions, circles are chance events. Work from right to left, calculating expected values at each circle.
Simulation uses random numbers to model many variables and produce a range of outcomes. It can be costly and is only as good as its inputs.

Dealing with risk and uncertainty in decision-making practice questions

Dealing with risk and uncertainty in decision-making in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Dealing with risk and uncertainty in decision-making: frequently asked questions

What is the difference between risk and uncertainty in ACCA PM?

With risk, you can assign probabilities to the possible outcomes, so you can calculate expected values. With uncertainty, you cannot assign probabilities, so you use decision rules or sensitivity analysis instead.

Which decision rule should I use in the exam?

Use the one the question names. If it asks which option a pessimist, optimist or regret-averse manager would choose, link them to maximin, maximax and minimax regret respectively. In a written answer, explain the attitude behind the rule.

How is the value of perfect information calculated?

Find the expected value if you always knew the outcome in advance, then subtract the best expected value you can get without that information. The result is the most it is worth paying for the information.

Do I need to learn simulation calculations?

Focus on understanding what simulation does, when it helps and its limits, because it is mainly tested in explanations. Be ready for simple questions on how random numbers are matched to probabilities if your study material covers them.