No σ for you!

[naddy]

Who had to die before \(\sigma_x\) could be added to the statistics functions of HP calculators?

I know approximately nothing about statistics, although I have encountered the standard deviation σ. The HP manuals helpfully explain the difference between the sample standard deviation \(s_x\) and the population standard deviation \(\sigma_x\). Whereas Sharp or Casio calculators from the 1980s would provide both functions, HP calculators invariably only provided s. This continued well into the models where you could no longer plead a lack of keys or other resources: The 32S, 42S, 28C/S, and 48SX all only provided s. It took until the 32SII (1991) and 48GX (1993) for σ to become available.

This feels like somebody didn't want σ to be readily available and it fell on the manual writers to explain how you could still calculate it.

Is there a background story to this?