HCD.23:5.2 - A missing explainer in an engineering studio
A studio uses a Jigsaw adaptation to compare three sensor arrangements. Each expert group prepares one arrangement’s measurement assumptions and failure, then teaches its home group. The supplied training case requires every reading of a known 10 mm displacement to be within 1 mm of the reference. Its qualified case sheet gives these constructed observations and conditions; they are not specifications for all sensors of the named kinds.
| Arrangement | Supplied result | Condition that changes its use |
|---|---|---|
| A: optical path | 9.6–10.4 mm with a clear path | An opaque guard blocks the path; the case supplies no usable reading then. |
| B: shielded electrical arrangement | 9.5–10.5 mm under the stated interference | This qualification requires verified shield continuity. |
| C: unshielded electrical arrangement | 9.7–10.3 mm in the quiet condition; 8–12 mm with the motor energised | The changed interference condition violates the per-reading tolerance. |
C’s prepared explainer is absent. In the receiving case the motor is energised and the optical path is blocked; B’s shield continuity has been verified. A learner suggests averaging C’s 8 and 12 mm readings to get 10. A substitute explainer uses the supplied criterion: the mean does not make either reading comply with the required 9–11 mm interval. B has the supported result under the actual conditions; C is not qualified by its quiet-condition performance. The listener identifies both the condition and the failed criterion, then makes their own supported selection.
The instructor needs five minutes at 14:50–14:55 to check and supply C’s permitted account and establish the replacement. Another prepared learner has finished their own home-group obligation by 14:45 and agrees to explain from 15:00 to 15:08. The three present recipients reserve 15:00–15:12: eight minutes for the explanation and questions, then four for each person’s written selection and ground. Preparation and movement are complete before 15:00. If that shared window or the prepared person is unavailable, this recovery has not been obtained.
The absent learner’s practice is separate. At 16:00–16:15 the next day, the learner and one willing classmate have a booked qualified tutor: five minutes to explain the original criterion, five for the listener to pose a changed condition, and five for feedback and the learner’s corrected return. The changed case switches the motor off and clears the optical path while leaving B’s shield status unknown. The learner now permits A or C under their supplied bounds and returns B’s missing qualification; the earlier choice of B is not repeated as a slogan.
The added allowance is twenty qualified provider-minutes: five for the initial repair and fifteen for the later tutoring. Added learner work is 74 minutes: three recipients at twelve minutes, eight minutes for the substitute, and fifteen each for the absent learner and returning classmate. Existing expert preparation is already part of the original studio design. A late replacement, further preparation or longer unresolved question changes this allowance. The first recovery supplies the remaining group’s comparison; the later exchange supplies the absent learner’s explanation and response to a challenge. Neither is inferred merely from receiving C’s case sheet.