Politically and Technically Correct ?

by: Grant Rule

The terms `man hour', `man day' and `man month' have been known to cause comment. Where necessary, I have long adopted the habit of using such terms as `work hour', `staff day' and `staff month' - I believe the intention is clear and it just avoids any possible issue.

However, there remains the technical problem: what on earth do the terms `staff day', `staff week' and `staff month' mean?

The answer? Very different things to different people. I make it a habit to collect such figures. Companies in the UK have variously told me they use `staff month' (or `work month' if you prefer) to imply anything from 108 work hours to 200 work hours (!!! Who are they kidding?), with a mean of 142 work hours. By the way, a `work hour' is an hour spent on productive work; that excludes lunch breaks, interruptions, comfort breaks, etc., but obviously the `product' resulting will vary. This essentially is the measure of expended effort known by the International Software Benchmarking Standards Group (ISBSG) as `Reporting Method C'.

A `staff day' may mean anything from 8, 7.5 or 7 hours spent physically present in the office (plus 2 to 3 hours of unpaid and unaccounted overtime), to the more realistic 5.2 or 6.5 work hours actually expended on productive work for the projects of concern.

As there is a 35% difference between the optimistic 8 hours and the more pessimistic 5.2 work hours per staff day, it seems rather important to have a `mutual understanding'.

So far as I am concerned, the only `safe' scale is `work hours' where we mean `an hour of effort spent on productive work'.

For estimating I would expect and plan no more than 5.5 work hours/staff day (unless the organisation has explicit procedures in place to maximise productive effort e.g. red/green time, `do not disturb' schemes, telephone rotas, etc.). This gives 110 work hours per staff month i.e. 5.5 work hours/day x 5 days/week x 4 weeks/month = 110.

Alternatively, 365 days/year less 52 weekends less 6 Bank Holidays less 20 days vacation = 235 staff days/year multiplied by 5.5 work hours/staff day = 1293 divide by 12 calendar months = 108 work hours/staff month (rounded). And many Europeans/British have more than 20 days vacation each year, so you could charge me with over-optimism!

However you work it, any expectation of more than approximately 110 hours of productive work in a period of 20 days `at work' is unrealistic. Differences in definition/meaning with respect to effort often far outweigh the range of error in functional sizing.