man-hour , or less person-hours , is the number of jobs performed by the average worker in an hour. It is used in written "estimates" to estimate the total amount of uninterrupted labor required to perform a task. For example, researching and writing a college paper may require eight hours of work. Setting up a family meal from scratch may require ten hours of work.
Working hours do not take into account the breaks most people ask for from work, e.g. to rest, eat, and other body functions. They only count pure work. The manager calculates the hours worked and increases the rest time to estimate the amount of time it takes a task to complete. So while a single lecture paper might take twenty hours of work, it almost certainly will not be completed in twenty hours in a row. Progress will be disrupted by work for other courses, food, sleep, and other distractions.
Video Man-hour
Real-world applications
The advantage of the concept of working hours is that it can be used to estimate the impact of staff changes on the amount of time required for a task. This is done by dividing the number of hours worked by the number of workers available.
This is of course appropriate for certain types of activities. It is most widely used when considering 'work', where the managed activity consists of separate activities that have simple dependencies, and where other factors can be ignored. Therefore, adding others to the packaging team will increase the team's output in a predictable way. In the transportation industry, this concept is being replaced by mile-and-ton-mile passengers for better cost accuracy.
In fact, other factors intervene to reduce the simplicity of this model. If some task elements have a natural time period, adding more staff will have a diminished effect: although having two chefs will double the speed of some food preparation elements, they roast chicken no faster than a chef. Some tasks also have a number of natural staff associated with it: the time to cut vegetables will be split in two with the addition of the second chef, but the time to carve the chicken will remain the same.
Another example is the saying, "Just because a woman can make a baby in nine months, that does not mean that nine women can make babies within a month." This saying is often cited in system development to justify the belief that adding more staff to the project does not guarantee that it will be completed more quickly.
Another problem with this model, as noted by Fred Brooks, is that organizational, training, and coordination activities can be more than the potential benefit of adding additional staff to a task, especially if it is considered only over a shorter period of time.
Maps Man-hour
Similar units
Similar concepts from man-day days, man-week , man-month , or man-year are used on a large project. This is the number of jobs performed by the average worker for a day, week, month, or year, respectively. The number of hours worked by individuals for a year varies greatly according to cultural norms and economics. The average annual working hours per person in employment as reported by OECD countries in 2007, for example, ranges from a minimum of 1,389 hours (in the Netherlands) to a maximum of 2,316 hours (in South Korea).
Productive system clock
The concept of productive clock system (PSH) has been used in forestry in Austria and with extension to other work. This includes the time for rest and can be used to calculate how long it takes to complete a task, including the required restoration time from physically challenging work, as well as the legal rest or other human interaction. If it includes a 15 minute break, it is written as (PSH15).
The related concept is a productive clock machine (PMH).
See also
- Henry Gantt
- Frank Bunker Gilbreth, Sr.
- Labor economy
- Mechanization
- Productivity
- Scientific management
- Excess value
- The Mythical Man-Month , Fred Brooks's classic book on software engineering
- Motion time and learning
- Frederick Winslow Taylor
References
External links
Man-year:
- Man-year is defined as 2000 hours: https://web.archive.org/web/20060722155057/http://www.onr.navy.mil/02/matoc/05_09/solicitations/docs/05-0002-02.pdf (Application Number 05-0002-02: Support Service for Naval Research Office for Legislative Affairs Office (Naval Office United States Naval Research: Arlington, Virginia, USA, 2004)
- Man-year is defined as 2087 man-hours: Report 5, Professional International And Technical Federation of Local Engineers 32: San Diego, California, 2000 (counts 311 "Unavailable/Unproductive")
Source of the article : Wikipedia
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