[ivansavz]

In summary, the difference between "fast" programmers and "slow" programmers is not 28 (as per Grant and Sackman folklore), but more in the range 1--7. Specifically, The work time variability tends to be larger for task type “test/debug” (SF50 = 2.4, SF25 = 3.2) and even more for “programming” (SF50 = 2.4, SF25 = 7.1) than it is for “maintain” (SF50 = 1.7, SF25 = 2.4) or for “understand” (SF50 = 1.8, SF25 = 2.9). Task type “review” is special. It exhibits both low variability (SF50 = 1.1, SF25 = 1.3) and low skewness.

[jsvaughan]

It also say this:

"Thus, if we ignore the most extreme cases, the differences between the slowest and the fastest individuals are by far not as dramatic as the 28:1 figure suggests"

Why would you ignore the most extreme cases?