Tablet holder for a care home: interpreting user trial evidence
Year 11 students at a Maltese secondary school are designing a tablet holder for a care home in Sliema. The brief: hold a 10-inch tablet at an angle between 30° and 70°, allow one-handed adjustment by residents with limited grip, be cleanable with alcohol wipes, and cost no more than €12 per unit for 24 units. The class has five weeks and workshop access twice a week with a pillar drill, scroll saw and hand tools; no CNC. Prototype A uses 18 mm plywood, two brass butt hinges and felt lining. In a trial with six residents, four could not move the hinge because it was too stiff, the felt absorbed disinfectant and stayed damp, and one unit tipped backwards when a resident pressed the screen. The teacher insists the next version must use standard bought-in components and be testable before the deadline.
1. Using the trial evidence, identify the three highest-priority design changes and explain how each change addresses a specific failure rather than a personal preference.
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The trial gives three distinct failures, so the priorities should follow severity and frequency, not ease of change. The hinge stiffness affected four of six residents, so it is the highest priority: the product fails its main accessibility requirement. A standard friction hinge with an adjustable knob or a ratchet hinge would let the user set the angle once and then move it with a larger handle; the specification should state a maximum operating force, e.g. 10 N at the tablet edge, tested with a spring scale. The damp felt is a hygiene risk, so the lining should change to closed-cell EVA or a wipe-clean TPU pad; the test is visual and moisture uptake after 24 hours. The tipping unit is a safety issue, although it happened once; it needs a wider base or a non-slip weighted foot, and a stability test with a 5 N horizontal push at the top. Changing all three at once would make the next trial hard to interpret, so prototype B should change the hinge and lining, and prototype C should add the base.
2. Write a revised product specification with measurable criteria and explain one trade-off you have accepted.
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Revised specification: (1) holds a 10-inch tablet, 250 mm × 180 mm × 8 mm, at 30°–70°; (2) angle adjustment force ≤ 10 N at the tablet edge for a user with 15 N grip; (3) all surfaces wipe-clean with 70% alcohol and no absorbent lining; (4) stable against a 5 N horizontal push at the top edge with tablet fitted; (5) unit cost ≤ €12 at 24 off; (6) made from standard components and ≤ 30 min assembly. Trade-off: choosing a bought-in friction hinge may cost €3.50–€4.50 each, which is a large share of €12, so the plywood body must be simplified or the finish left as sanded and sealed rather than veneered. I would accept a slightly larger base footprint to gain stability because the care home has 450 mm deep bedside tables, so a 220 mm base still fits. The €12 target is not a reason to keep the unsafe tipping design; if the hinge pushes cost over, the class should ask the client whether 20 units at €13 is acceptable, because the brief's main purpose is safe one-handed use.
3. Describe a test plan that would give trustworthy evidence in the two remaining workshop sessions.
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Test plan: use the two sessions for a controlled comparison. Session 1: make three prototype B units with the new hinge and three C units with the wider base, all otherwise identical. Recruit six residents, but use the same six as before so differences are not confused by different grip strength. Test 1: ask each resident to change angle from 30° to 70° and back, record success/failure and force with a spring scale; repeat three times. Test 2: stability-place tablet in holder, apply 5 N horizontal push at top edge, record tip/no tip. Test 3: wipe the lining with alcohol, leave 10 minutes, check for moisture and surface damage. Session 2: repeat with a second group of four residents to check the result is not specific to the first group. Record results in a table and set a pass criterion before testing, e.g. five of six succeed and no tip. This gives evidence for the final choice rather than opinion.