Design justification CER
Tue, Dec 8, 2026 · Week 16 · Principles of Biomedical Technology (Principles of Biomedical Science)
Today's goal: Students write a CER justifying their app design choices against user needs and usability principles.
This is a model of the work you should turn in today. Use it to check your own: match the structure and the level of detail, do not copy it. Your data and wording should be your own.
Claim: Our lobby wayfinding kiosk design meets the navigation needs of our two target users at a large hospital, an older first-time visitor named Ellen and a hurried delivery driver named Marcus.\n\nEvidence (persona and feature list): Ellen needs to reach a department she has never visited and reads slowly, so we made the home screen a single large question, "Where are you going?", with a short list of the most-visited departments in big high-contrast text. Marcus needs the loading dock and its entrance quickly and only glances at the screen, so we added a persistent "Deliveries and Dock" button in the same fixed spot on every screen and a printable step-by-step route card.\n\nReasoning (tie each choice to a usability principle): The single-question home screen serves simplicity, because it removes competing choices and shows one clear task at a time. The big high-contrast text serves accessibility, so a user with weaker vision like Ellen can still read it without help. The fixed-position "Deliveries and Dock" button serves consistency, because Marcus can find the same control in the same place every time and does not have to relearn the screen. The printable route card serves memory support, so a user does not have to hold every turn in their head while walking a long hallway.\n\nPrediction: Because the design cuts the reading load and the number of choices that usually make people freeze or ask staff for help, more visitors should reach the right department on their own and fewer should crowd the information desk, which is the behavior change we want in a busy lobby.\n\nAssumptions and limitations: We assume our two personas represent most kiosk users, that visitors can stand and touch a screen, and that department names on the kiosk match the signs in the hallways. If many users are in wheelchairs and cannot reach a tall screen, or if the building signs use different names than the kiosk, then the design would fail those users and our claim would need to change. A lower screen height and matching signage would matter more than any button we added.
This model shows the level of evidence and organization needed to complete: Parallel worked model of a design-justification CER: for a different product (a hospital lobby wayfinding kiosk), it traces each design choice to a persona need and a usability principle, predicts the effect on behavior, and states assumptions and limitations, so students see the format and depth without seeing an answer to their own clinic-app prompt.
- Write one defensible claim.
- Choose specific evidence that supports the claim.
- Explain the scientific rule that connects the evidence to the claim.
Keep the structure. Replace the question, facts, measurements, and evidence. Then recheck units, vocabulary, and whether the conclusion goes beyond the evidence.
Also due today: Submit your CER on the class site, or hand it to Mr. Mendoza in class before end of period.
Claim ceiling: Today's evidence supports a classroom claim about design justification CER. It cannot prove causation, diagnose a real patient, or justify action outside this room.
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.
It builds this reusable test skill: Justifying a design choice by tracing it to a user need and usability principle.
- Name the concept or data pattern being tested.
- Cross out choices that violate that rule or the evidence.
- Justify the best remaining choice before checking the answer.