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Question 1) So lets say we have a wall that is 400 sf of area. Lets say one labor can produce 40 sf of wall per day. Then we have 400/40=10 days for 1 labor to build this wall. So this is the duration required to build this wall. Is this also equal to work now? Because work = duration x units, so, 10x1 = 10 days = 80 hours?

Question 2) Now, if we had a labor that could produce more, say, 50 sf of wall per day, then we have 400/50= 8 days to complete the wall, which is the duration. But now with same logic the work is changed to 8days x 1 unit = 8 days = 64 hours.

So we have the same wall, but depending on the skill of the worker, the amount of work is different. It doesn't make sense to me that the amount of work required to produce the wall is different in both cases. It is the same wall. Why the amount of work to build it is different?

OR

What I should have done in the second question was, saying that the more skilled resource is 50/40 = 1.25 times more effective, so, when calculating the work, I should have said 8days x 1.25 units = 10 days = 80 hours again? Because the skilled unit is worth 1.25 of first unit? - If so then it makes sense. This is the way we should think correct?

EDIT: I am asking the question from simply the point of view of proper project management practices and Earned Value Analysis (EVA) purposes only. Such as in Work = Units x Duration. The question is not in broader context of life. Simply in the context of EVA in project planning. That's all.

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  • Can you maybe add some more information, how you arrive at your conclusions/questions? I just revisited my old textbook samples and none of them talk about "work" or "hours" for EVA the way you do. They all talk about planned value and current value and how you can calculate how much behind/over budget your project is. But none of them use hours except for the initial calculation of planned value.
    – nvoigt
    Apr 19 at 13:36
  • You are confusing concepts. What you talk about is different. You are talking about the overall performance measurement, such as by forming the S-Curve by taking the cumulative of earned values and planned values and costs. That is where you use what I am doing here. That is one level higher than this. But to do those, in other words, to come up with those planned or current values, actual costs (PV, CV, AC) etc... you must know the work and resource amount of activities, from the step I described. i.e. multiply the resources by the rates, to come up with a cost of activities Apr 19 at 14:00
  • You seem to be looking more for confirmation than an answer and your summary is completely incorrect. Your paragraph after the "OR" is mind boggling. The answer you're looking for is variability. And you use variability, also known as CPI and CV, to estimate remaining work, not this spaghetti analysis in your question. Apr 20 at 13:38
  • My summary is completely correct. my question is simple but completely logical fundamental question.. Sorry to boggle your mind with the most the fundamental work formula, which is used by millions except you.. My question has no relation whatsoever to what you bring as variability. CPI and CV is also totally irrelevant here . They are used in overall performance measurement as I explained above. I am simply doing work amount calculation of a 400 sf wall here and you talk about variances, CPI and CV and so on... LOL.... Apr 20 at 16:06
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This is the way we should think correct?

That depends entirely on your type of project. Most likely, no, this thinking is way oversimplified and will lead you to operate on numbers that do not reflect reality.

A woman can deliver a baby in nine months, two women can not deliver a baby in four-and-a-half months.

A skilled woman will not be able to deliver a baby in 8 months. Even if she is experienced (let's call her a "senior woman", no offense meant) and had babies before.

Not everything is as complicated as creating new life, some labor is really that stupidly boring that you can plan it as you did. But then, that planning has been replaced by computers years ago. So your little math examples work out as homework to practice for the rule of three. But in the real world, planning a project is more complex than that.


That said, to answer your question:

Why the amount of work to build it is different?

The same way that if you drive 100mph instead of 50mph you will be in the next city in less time. It's still the same distance though. You just got a machine with different settings. Or a machine at all. You could have walked for days to reach the same city. The actual work you put in has little to do with the end result. A wall can by built in many different ways, with many different variables. "Hours worked" is just one variable and probably not even the most significant one. Work cannot be measured in hours alone, which is why when you look at hours alone, it looks weird.

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  • thanks but I am not asking the question within a broader context or general life philosophy etc.... I am asking the questions simply from proper project management and earned value analysis (EVA) point of view. Could be simplified in relation to real life, yes, but that is not the point. I am simply asking as far as EVA is this ok (the last thing I wrote for question2). And yes work is measured in hours in EVA. Go to MS project for instance, and check the work column, it will show you hours. I am asking from simple context of work = duration x assigned units.... This is all. Apr 19 at 11:31
  • I think your question could be improved if you added this context to the question.
    – nvoigt
    Apr 19 at 11:32
  • Thanks. I did it. Apr 19 at 11:36
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Work is probabilistic. There is always variability in work efficiency caused by an unknown number of variables, including skill, but also including random noise. An individual will also produce variable outcomes doing the same work.

Also, duration = hours under few circumstances. None of us is 100% productive when we work. So if the duration equals five days, it is unlikely that the hours to produce that work equaled 40 hours. Most likely, it equaled probably half of that.

All tasks come with differing degrees of resource elasticity. That's another thing to consider. Some tasks will respond quite favorably adding resources to it, while other tasks will will not respond at all or even get worse in duration. It is a mistake to assume no task will respond to adding resources. You have to analyze the task on a case by case basis, both the task itself and the environment in which the task is performed.

Overall, you over simplified the examples you provided; however, you are also touching on the complexity of how work, duration, and resources play together and how you analyze such things when estimating work. This is both a science and art.

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  • thanks but I am not asking the question within a broader context or general life philosophy etc.... I am asking the questions simply from proper project management and earned value analysis (EVA) point of view. Could be simplified in relation to real life, yes, but that is not the point. I am simply asking as far as EVA is this ok (the last thing I wrote for question2). I am asking from simple context of work = duration x assigned units.... Apr 19 at 11:32
  • That formula is generally correct; however, if you are approaching EV with this simplicity, then your results, at best, will be unreliable and, at worst, hilarious. This is complex. And you're touching on it because YOU brought in the context of a higher performer, not just a simple formula. On the surface, EV is simple. In practice, producing results you can use, it is everything but simple. Apr 19 at 11:52
  • I am not asking if the formula is correct. It is correct. And this is simply how it works in EVA. I placed an edit at the end of my question to make sure that everyone knows my question is in EVA context and nothing more general. Thanks for the answer. Apr 19 at 11:58
  • Yeah, EV does not work like that. You literally asked, "Why the amount of work to build it is different?" The answer is because it does not work like that because of variability, which both @nvoigt and I answered. If you do not adjust that formula considering the broader, and I guess in your world more philosophical, context, you are doing it wrong. Apr 19 at 12:01
  • I didn't ask like that at all... I pointed out the difference and proposed the correct way in the end... and trying to confirm if that is ok... Read the question again. And yes in EVA work = duration x assigned units to the task,. May be you can enlighten me with a broader formula? Which would make all the texts in EVA and project management obsolete Apr 19 at 12:05

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