ENGR-111 Introduction to Engineering

In-Class Work 3: Decision Matrix

We do this live in class. Small breakout rooms, about 30 minutes. I’ll tell you the exact time in class. A spreadsheet template for the matrix is here; use it, or any spreadsheet, or a table typed into the submission box.

The problem. Your group runs a small company. A customer wants a way to keep a bicycle dry and secure outside an apartment building in Oregon, year round. Budget is $300.

1. Write the specifications. ~5 minutes.

Pass or fail requirements that any solution must meet. Each one needs a number and a unit. “Secure” is not a specification; “cannot be opened without a key or a code” is. “Survives winter” is not; “outdoors, unheated, October to March” is.

2. Come up with three different designs. ~10 minutes.

Three different operating principles, not three sizes of one idea. Test: would they fail for different reasons? Include the off-the-shelf option.

3. Screen them. ~2 minutes.

Drop any design that fails a specification. If nothing survives, check your specifications. If everything survives, they may be too loose.

4. Write your criteria and weight them. ~5 minutes.

Criteria are how you choose among the designs that passed: better or worse, not pass or fail. Three or four.

• Look at performance (how well), cost (how cheap), and schedule (how soon), and at what actually differs between your designs. Cut any criterion all three would score the same on
• For each criterion, state which direction is better, what unit you are counting in, and where the number comes from. Example: “cheaper is better, in dollars, from a hardware store website”
• If a criterion has no unit, such as “looks acceptable to the neighbors,” decide what you will count instead before you score
• Weights add to 100

5. Score and total. ~8 minutes.

Score each design 1 to 5 on each criterion. 5 is always the good end, including for cost. Score one criterion at a time across all three designs. Mark which scores were guesses.

Then answer: is the winner the design you would build? If not, is a weight wrong, or is your instinct wrong? Change a weight only if you can say what you learned.

Each of you submits the group’s answer. Type it into the Moodle submission box:

• First line: everyone’s full names
• Second line: the design that won
• The group’s specifications, one per line, each with a number and a unit
• A description of each of the group’s three designs
• Anything the group screened out, and which specification it failed
• The matrix: criteria with weights, scores 1 to 5, and totals. Paste it in as a table, or attach a screenshot or photo of the group’s spreadsheet
• Did the matrix pick the design the group actually wanted? If not, what did the group do about it? A few sentences

Grading. Everyone in the group gets the same score. If you do not submit, you get no credit for that session. Grading and the AI policy are in the syllabus. Specific to this one: a specification without a number does not count, and three designs that fail the same way count as one. I read the last item most closely.