Quantest

What the data showed

Working notes from building the platform: how the data is recorded, the bugs that produced wrong numbers, and what we changed so they could not happen twice. No tips, no calls, no performance figures.

A 1901 colour lithograph: a bull in a checked coat blows soap bubbles labelled “inflated values” while a crowd of people reaches up to catch them.

Never draw a pattern across a missing bar

A detector cannot see a hole. Non-adjacent bars read as adjacent in a list, and the measurements that define a pattern are taken between bars.

 Looking up at the Bombay Stock Exchange tower on Dalal Street, Mumbai, with a live LED ticker running across its facade.

When 98% complete is incomplete

One rate-limited request out of sixty put the wrong day's move in the header of every page. Here is why a percentage was the wrong test.

 A late-19th-century Japanese woodblock print of the Dōjima rice exchange in Osaka.

Beta is not one number

The same 517 stocks, the same benchmark, the same year. Measured daily and weekly, the two betas correlate only 0.757.
A 1907 pen-and-ink cartoon titled “The Tapeworm”: top-hatted brokers walking a ticker-tape ribbon through a broker's office and a crowd in the street.
“The Tapeworm”, Frank Arthur Nankivell, 1907.
In investing, what is comfortable is rarely profitable.Robert Arnott