Welcome
Evaluate alternatives and justify the preferred engineering solution
In Lesson 04 you developed several alternative solutions to a comparable level of technical detail. The next step is to decide which option should move forward.
Professional engineers do not choose a preferred solution simply because they like it. They use a feasibility study to compare alternatives against relevant criteria such as technical performance, cost, resources, risk, time, sustainability and compliance.
How can an engineer use evidence to decide which alternative is the most feasible and justify the preferred solution professionally?
Learning Outcomes
What should you know and be able to do by the end?
Learning Aim A requires you to investigate possible solutions and select an appropriate engineering solution. Your decision should be supported by clear evidence rather than personal preference.
Prior Knowledge Check
Connect scoped alternatives to feasibility analysis
Answer these three questions before beginning the main learning.
Why This Matters
A good idea is not automatically a feasible project
An engineering concept may perform well in theory but still be unsuitable for the project if it exceeds the budget, requires unavailable equipment, cannot be completed in time, introduces unacceptable risk or creates maintenance and sustainability problems.
Feasibility studies help engineers make controlled decisions before significant time and money are committed.
A concept gives the highest predicted technical performance but costs three times the available budget and depends on a specialist component with a 16-week lead time. Should it automatically be selected? What evidence would you examine before deciding?
Main Learning Content
A3 • Feasibility studies and preferred-solution selection
1 • What is a Feasibility Study?
A feasibility study is a structured investigation that asks whether a proposed engineering solution is realistic, achievable and suitable within the project's constraints.
Can it work?
Technical performance, reliability, safety and compatibility.
Can we deliver it?
Time, people, facilities, equipment, skills and supply chain.
Should we do it?
Cost, risk, sustainability, benefits and stakeholder value.
2 • Core Feasibility Criteria
Technical
Can the solution meet the engineering requirements?
Click to explore- performance
- accuracy
- strength
- reliability
- compatibility
- testability
Financial
Can the project be delivered within the available budget?
Click to exploreConsider materials, bought-in components, specialist services, tooling, labour, operation and maintenance.
Resources
Are the required people, equipment and facilities available?
Click to exploreConsider workshop capability, CAD/CAM access, testing equipment, skills, technicians, suppliers and lead times.
Time
Can the alternative be completed within the project schedule?
Click to exploreCheck design effort, procurement, manufacture, assembly, testing, refinement and contingency time.
Risk & Safety
What could prevent success or cause harm?
Click to exploreConsider technical failure, supply risk, safety hazards, uncertain performance and dependency on unfamiliar technology.
Sustainability
What environmental and lifecycle impacts are important?
Click to exploreConsider energy use, materials, waste, repairability, service life, recycling and responsible sourcing.
3 • Decision Matrices
A decision matrix provides a transparent way to compare alternatives against the same criteria.
- Choose relevant criteria.
- Apply a weighting if some criteria are more important than others.
- Score each alternative using evidence.
- Multiply score × weighting.
- Compare totals and investigate any surprising result.
A decision matrix supports judgement; it does not replace judgement. Poor evidence, unrealistic scoring or inappropriate weighting can produce a misleading result.
4 • Justifying the Preferred Solution
A professional justification should explain why the selected alternative provides the strongest overall fit with the project requirements. It should also acknowledge important disadvantages or remaining uncertainties.
“Alternative B is selected because it meets the required load and safety performance while remaining within the available budget and workshop capability. Although Alternative A offers greater automation, its higher cost and specialist components increase delivery risk. Alternative C is lower cost but does not meet the required lifting range.”
5 • Avoid False Precision
If evidence is incomplete, say so. A score of 8/10 is not automatically more scientific than a clear qualitative judgement. Record the basis for each score and identify where further testing or supplier information is needed.
Lesson Presentation
Teacher-led A3 learning
Feasibility Studies & Selecting the Preferred Solution
Use the Unit 5 Lesson 05 presentation during the teacher-led part of the lesson. This presentation develops feasibility criteria, option comparison, decision matrices and evidence-based solution selection.
▶ Open Lesson PresentationEngineering Case Study
Smithsons • Comparing three product directions
Which fitness product concept should move forward?
Smithsons has developed three alternatives: a wrist-worn tracker, a clip-on tracker and a hybrid watch. The team now needs to select the most feasible option.
Alternative A • Wrist Device
Strong user appeal and display capability, but moderate cost and battery demand.
Alternative B • Clip-On Tracker
Low cost, simple manufacture and low power demand, but fewer features.
Alternative C • Hybrid Watch
Strong brand fit and premium appeal, but complex packaging and higher development risk.
Which criteria should carry the highest weighting for Smithsons? Would the answer change if the business priority were low cost, premium branding or fastest route to market?
Case-study task
- Select five feasibility criteria.
- Assign a weighting to each criterion.
- Score Alternatives A, B and C.
- Calculate weighted totals.
- Write a short justification for the preferred solution.
- State one limitation of your comparison.
Feasibility Study Activity
Compare alternatives using evidence rather than preference
Scenario: Moving a 25 kg Component
Three alternatives are available: a wheeled lifting trolley, a guided rail system and a compact powered lifting aid. You must recommend one option for development.
Select at least six criteria from technical performance, safety, cost, resources, manufacture, time, maintenance, sustainability and risk. Give each criterion a weighting.
Score each solution using the technical information developed in Lesson 04. Explain the evidence behind each important score.
Write a concise engineering justification for the preferred option. Include at least one disadvantage or remaining uncertainty.
Lesson Summary
Key learning from Lesson 05
1 • Feasibility is Multi-Factor
Technical performance matters, but so do cost, resources, time, risk, safety and sustainability.
2 • Compare Consistently
Use the same relevant criteria for every alternative and support important scores with evidence.
3 • Weightings Reflect Priorities
Some criteria may matter more than others, but weightings must be justified.
4 • Selection Needs Justification
The preferred solution should be chosen because it provides the strongest overall fit with the project requirements, not because it is your favourite.
Lesson 06 is the Learning Aim A Assignment Workshop, where you will organise, develop and quality-check your Aim A evidence.
Exit Ticket
Show what you have learned
Question 1
What is the purpose of an engineering feasibility study?
Question 2
Name four feasibility criteria that could be used to compare engineering alternatives.
Question 3
Why can a weighted decision matrix be useful, and what is one limitation?
Question 4
What should a strong preferred-solution justification include?
Check answer guidance
Q1: To determine whether an alternative is realistic, achievable and suitable within project constraints.
Q2: Examples include technical performance, cost, time, resources, risk, safety and sustainability.
Q3: It provides a transparent comparison, but results depend on the quality of evidence, scoring and weighting.
Q4: Evidence showing why the option best meets the project requirements, plus important disadvantages or uncertainties.
Worksheet 5
Feasibility Studies & Selecting the Preferred Solution
Unit 5 Lesson 05 Worksheet
Complete the worksheet to practise feasibility analysis, weighted decision making and evidence-based preferred-solution selection.
The Lesson 05 worksheet and teacher answer file can be added to these folders when the resources are ready.
AI Lesson Companion
Future VITHAAA learning support
Ask VITHAAA AI
The future Unit 5 AI Tutor can challenge feasibility assumptions, ask for evidence behind scores, test whether criteria and weightings are reasonable and help students strengthen their justification without selecting the preferred solution for them.