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How quality is controlled
An explanation is only useful if it is correct. This is what is checked in every lesson, what is being introduced and what still has limits.
Already done
Before a lesson is published
A single source for every figure
All the numbers in a lesson come from one calculation. The voice, the formulas and the drawing cannot say different things.
Two routes that must agree
Each problem is solved by two methods and the results have to match.
A second, independent solution
The problem is solved again separately and the results are compared with those of the lesson.
Reviewed by a person
Before it is published, every lesson is reviewed by someone trained in the subject.
Being introduced
What comes next
- Checking against the official marking criteria, where they exist.
- Verifying the results with symbolic computation.
- Automatic checking of the audio by transcription.
After publishing
If there is still a mistake
- Every lesson has a «Report a mistake» link.
- Corrections are recorded in a log.
- If the lesson came from a paid request, its price is returned to the credit.
Frankly
The limits
The voices are synthetic
Lucy and Dan are computer-generated voices reading a written script. They may mispronounce the odd word or symbol; the subtitle always shows the correct text.
The lessons are translations
The English lessons are translated from the Spanish originals, and the exam questions themselves were set in Spanish. Notation and conventions follow the original exam where they differ from those used elsewhere.
These checks reduce mistakes, but they do not rule them out. The lessons are study support and do not replace the official marking criteria.
Who is behind it
Juan Carlos del Río
The lessons are prepared and reviewed by someone trained in engineering, physics and mathematics. The approach is that of someone who had to understand these problems, not just pass them: first the why, then the sums.