From your answers to the figure on the certificate
Nothing in the pipeline is hidden. The score report prints every intermediate value so you can follow the arithmetic.
Weighting
Each item carries one, two or three points by difficulty, totalling 38 across the paper. Correct answers add their weight; wrong and blank answers add nothing.
Selecting the norm table
Your age band, education level and area combine into an expected mean expressed as a fraction of the maximum, with a standard deviation of 17 per cent of the maximum.
Converting
Your standard score is the distance from that mean in deviations. Multiply by 15, add 100, clamp to the 55 to 145 reporting range, and read the percentile off the normal curve.
Scored against age, education and area norms. Free certificate with a QR code anyone can verify.
Questions people ask
Why clamp at 55 and 145?
Beyond three deviations a twenty-item paper cannot discriminate meaningfully, so reporting a figure there would be false precision.
Are the norms empirical?
They are indicative tables built for this instrument, described as such on every report and certificate.