Sure they can. Abs(). Or if you prefer to not have quite so much micro-nano, you could also use Cumulative Distribution Functions [1] which are basically just sums of Probability Density [2].

Are they a 4σ programmer, 1σ programmer, -0.5σ programmer, -2σ programmer?

Plus, most people are "average" not negative productivity, and CDFs let you use really fun stuff like Beta Distributions (variable, shapable distributions) and Gamma Distributions (exponential distributions). They're super sweet as far as probability statistics.

[1] https://en.wikipedia.org/wiki/Cumulative_distribution_functi...

[2] https://en.wikipedia.org/wiki/Probability_density_function

[3] https://en.wikipedia.org/wiki/Beta_distribution

[4] https://en.wikipedia.org/wiki/Gamma_distribution