Weighting oral and written evidence in the external assessment
The external assessment for this subject comprises an oral examination and a written examination. A student, Priya, performs strongly in the oral (estimated 80%) but weakly in the written (estimated 50%). Her teacher is asked to predict her overall external result and to advise her on where to focus in the final weeks. The teacher knows the external oral and written components carry fixed weightings within the external assessment, and that the school-assessed component is separate and already submitted. Priya believes that because the oral is 'worth more', she should do no further written preparation.
1. Explain why Priya's belief that she should abandon written preparation is likely mistaken, using the concept of weighted components.
Read the worked answer
Priya's reasoning confuses performance level with marginal gain. Even if the oral carries substantial weight, she is already performing at 80% there; further oral work has a high baseline and limited headroom. Her written performance at 50% has much more room to improve, and each percentage point gained on the written component translates into overall marks according to its weighting.
If, for example, the oral and written were weighted 30% and 70% within the external assessment, a 10-point gain on the written would add 7 points to the external score, whereas a 10-point gain on the oral would add only 3. The correct strategy is to compare weight × headroom, not weight alone. Abandoning the written component would leave the larger weighted component underprepared.
She should also note that the school-assessed component is already submitted, so all remaining effort should target the external components.
2. Suppose the external oral is worth 30% and the written 70% of the external assessment, and the external assessment is 30% of the overall grade. Calculate Priya's overall external contribution if she improves the written from 50% to 60% while the oral stays at 80%.
Read the worked answer
External score before improvement:
- Oral: 80 × 0.30 = 24
- Written: 50 × 0.70 = 35
- External total = 59%
External score after improving the written to 60%:
- Oral: 80 × 0.30 = 24
- Written: 60 × 0.70 = 42
- External total = 66%
The external assessment contributes 30% of the overall grade, so the gain of 7 external percentage points is 7 × 0.30 = 2.1 overall marks. The same 10-point gain on the oral would have produced only 10 × 0.30 × 0.30 = 0.9 overall marks. This confirms that the written component offers the greater marginal return, and Priya should redirect her final preparation accordingly.