[projectramo]

I think they still found a large difference between the best and worst developers. Another summary (quotes that I can't seem to format):

The main findings from this investigation of the dataset variance.data can be summarized as follows:

  The interpersonal variability in working time is rather dif- ferent for different types of tasks.

  More robust than comparing the slowest to the fastest in- dividual is a comparison of, for example, the slowest to the fastest quarter (precisely: the medians of the quarters) of the subjects, called S F   .

  The ratio of slowest versus fastest quarter is rarely larger than 4:1, even for task types with high variability. Typ- ical ratios are in the range 2:1 to 3:1. The data from the Grant/Sackman experiment (with values up to 8:1) is rather unusual in comparison.

  Caveat: Maybe most experiments represented in variance.data underestimate the realistic interper- sonal variability somewhat, because in practical contexts the population of software engineering staff will often be more inhomogeneous than the populations (typically CS students) used in most experiments.

  Still only little is known about the shape of working time distributions. However, variance.data exhibits a clear trend towards positive skewness for task types with large variability.

  The effect size (relative difference of the work time group means) is very different from one experiment to the next. The median is about 14%.

  The oft-cited ratio of 28:1 for slowest to fastest work time in the Grant/Sackman experiment is plain wrong. The cor- rect value is 14:1.