# PMI PMP Project Management Professional – Introducing Project Schedule Management Part 3

**Considering Leads and Lags**

I mentioned leads and lags a little bit earlier in this section, but it’s really important to have a good grasp on what’s a lead and what’s lag, because you will see some questions on these for your exam. These are values that you add to an activity to change or affect its start time.

So lead time and lag time. Lag time is positive time that you’re taking that start time and you’re moving it away from its scheduled start time. Lead time is negative time that you’re taking that start time and you are subtracting, you’re moving it closer to the project start time. So it’s done on an activity that you’re moving an activity, you’re delaying it or you are increasing you are moving it closer to where we are today. So sometimes lead is called accelerated time. Lead can even allow activities to overlap. Lag time is just the opposite. It’s waiting time. It moves activities further apart. So lead time and lag time. Let’s take a look at our lead time. Procurement takes 30 days.

We’ve already talked about this, right? 30 days for procurement, you need your cabinets in 45 days. So on day 15, you order the cabinets to have them delivered on day 45. So it’s a way of saying that I don’t start that process on day 45. It’s as if I need the cabinets on day 15. So I have a lead time for my cabinet delivery of 45 days, even though it will take 30 days to get out there. So on day 15, I have 30 days. I need them on day 45. I don’t need them today. I can’t really just stick them somewhere they’re going to be, someone’s going to steal them or get damaged. I want them delivered on day 45.

So it’s as if I’m coming back in time, as if I need them today, even though it takes 30 days to get here. So lead time is any time you move activities closer, it’s negative time because you’re coming back in the schedule 30 days. In this instance, 30 days from day 45 is when you start the cabinet delivery or cabinet procurement activity. Another lead time example here is with painting.

So we want to paint a big hotel room. The priming crew, they start on day one and as soon as they’re finished, then we can start painting. So we have a finish to start primed to paint. So technically, the painting crew can chase the priming crew around, so they can have a lead time of 19 days. I don’t have to have all of the rooms primed in order to start painting. So on my painting activity, it’s scheduled to start on day 20. But really it can start one day after all of these activities are done. So even though it is a finish to start, I can say -19 days to start 19 days sooner than day 20.

So it can chase the primers through the hotel. Lag time is anytime you’re waiting, so you’re waiting for materials to cure, like paint or concrete, or you have to wait for something to calm down or to cool off or whatever the case may be. In your waiting time, it’s plus time. So you take a start date. You could add plus two to it, and that pushes it out. So lag time increases duration. Lead time reduces duration of the whole project. It’s a schedule compression technique, so know those terms for your exam. Lag in lead. Lead negative time. Lag positive time. All right, good job. I’ll see you in the next lecture.

**Estimating Activity Durations**

So far in our schedule management, we have identified the activities, then we have put those in the order in which they should happen. Now we need to predict how long will each activity happen. So that gives us the duration. So estimating activity duration is we’re talking about called predicting duration for task. So the level of detail that you have available, depending on how much detail you have available, will determine how accurate your estimates are. So are they really high level and kind of dreamy? Have you done this type of work before? So you have proof?

So how do you know how long an activity should take? The activity list is what we’re examining here. We’ll get our activity list and we’re going to look at each activity and say how long each activity should take place. Now, I may not always know that I may need to rely or probably will rely on my project team or experts or organizational process assets, some history. I also have to consider what resources will I use on the activity? Do I have a piece of equipment that can really get stuff done quickly? It’s a big powerful piece of equipment, can really rip up the ground. Or am I forced to use a small tiny piece of equipment that’s slower? So the resources that I could use can also affect duration.

Are there any other special attributes I need to know about that could affect duration? Like we’re painting the wall, but when we paint the wall, it takes a very special process and you have to paint it four or five times and you have to sand it and it’s a glaze that goes over it. So that that may affect duration because it’s some waiting time and the humidity can affect it. And there’s a lot of unknown factors with that type of work. What about resource capabilities?

A senior engineer versus a junior engineer? And this is really what I was talking about a moment ago with that piece of equipment. If I hop back up to activity resource requirements, I got ahead of myself. Requirements means I have to have this particular resource and that can affect my schedule. So I have to have a particular type of wood, or I have to have a piece of software or a particular piece of equipment. We have to procure it, or somebody else is using that resource right now and I need it in order to do my activity that can affect the duration. And then of course, OPA, I can go back to historical information and then from that I can have more accurate predictions of duration based on what happened in other projects in the past.

Our edo’s for estimate activity duration, our inputs, the PM plan which we need, the scope management plan and the scope baseline, my project documents, activity attributes, the activity list we just created, your assumption log lessons learned, register the milestone list, the team assignments, the resource breakdown structure, which we’ve not seen yet. The resource breakdown structure, I’m going to tell you it’s just a hierarchy like the WBS, but it shows what resources are used where. So a resource breakdown structure can help me predict duration based on what resources I’m using and where in the project resource calendars, when people and resources are available, what are the requirements I need on each activity. So as far as resources go, materials, equipment, specific people, my risk register because risk can affect time. And then EEF and OPA tools and techniques here to estimate expert judgment, analogous estimating, parametric estimating, three point estimating, and bottom up estimating.

We’re going to look at all of those data analysis, alternative analysis and reserve analysis, decision making and meetings. So we’re going to talk about all of that business here when it comes to estimating a lot of terms in this tools and techniques section. My outputs of estimating, the activities I get, my duration estimates, the basis of estimates, and I may have some updates to my project documents. Like activity attributes, the activity characteristics may need to be updated, the assumption log and the lessons learned register. So how do I go about creating duration estimates? So we’re trying to predict the activity’s duration. We’ve already put them in order. Now, how long will each activity take? Well, the tasks are first identified. We’ve done that. We’ve created the activity list, we’ve looked at the sequencing of the activity.

So we’ve done that. Now we need to say, well, what resources do I need to do these activities? People, material, equipment, things that could affect the duration. Then when I know that information, I can begin to predict how long each activity would take. And then activities, these four activities are iterated. So as I move through the project, these four activities happen over and over and over. So if I have a change in my scope, that’s probably going to mean more work. So identify the task, I put them in the order, identify resources, and then predict. So if you’re doing rolling wave planning, the four activities are iterated. So you do these over and over and over as needed. And the output of this is to predict how long each activity takes. And then we can begin to predict how long the project will take and have a very accurate estimate. Some things that I need to consider when it comes to estimating duration the law of diminishing returns.

The law of diminishing returns basically tells us you can only get so much yield, so much return when one factor remains the same. So the classic example is you have a wheat field to harvest the yield. There’s only so much wheat that will come out of that field. Just because I add more and more labor doesn’t mean that yield is going to increase. It might mean I get done faster. However, at some point we can’t just keep adding labor. I can’t say, well, ten people can do it in 8 hours, so let me add 20 people and they’ll do it in 4 hours. Oh, let’s do it with 40 people and do 2 hours or 80 people in 1 hour. It just doesn’t work that way. It’s like the old PM joke, you can’t have nine women get together and have a baby in a month. That some things take a set amount of time. The law diminishing returns is that you can’t continue to add labor. You can’t keep adding labor and labor and labor to drive the duration down.

That doesn’t always work. So the number of resources won’t reduce duration. Advances in technology, though, you might have faster equipment. So that’s great. You might also get over the learning curve. A lot of times the learning curve, we think, oh, we’re learning to get better. In reality, the learning curve is a dip in production to get better. So the dip that you take, you have to climb out of because it’s a new software or new hardware, new equipment. So for example, if you are on a Windows machine, you’ve never worked on a Mac before and now you get a Mac.

You have to learn how to use a Mac. So how to use an Apple, the old Apple SC two, that was my baby back in the day, if you want to call it a Mac. But my point being, if you’ve never worked with that hardware or that software, and you’re really efficient now, when you go to the new hardware software, then you go down in productivity and you have to learn your way back to your old level or exceed your old level of productivity. So that’s the idea of the learning curve.

So at some point you have this idea of overcoming the learning curve. The learning curve also tells us that as we repeat the same types of activities over and over, I’ll become more efficient. So if you have, let’s say, 500 tables or desks that you have to assemble, that’s your project. And you go out with the team and you begin installing to predict how long it will take. So you put one together and it took 2 hours to do. It was this very complicated piece of furniture that you’ve got to install.

So it took 2 hours to do. Well, you walk away from that and you say, okay, we’ve got 2 hours and 500 to do. So that’s going to be 10,000 or 1000 hours, hopefully not 10,000. So 1000 hours because the first one took 2 hours. Won’t they all take 2 hours? Well, no, because you’re going to begin to develop a system pretty soon. You’re not even going to have to look at the directions. You know exactly how it snaps together.

That’s a good example of the learning curve as well. And then we have what’s called Parkinson’s Law or the Student syndrome. Parkinson’s Law says that work will expand to fill the time allotted to it. So if you ask me, Joe, how long will it take to do this task? And I say it’s going to take 40 hours. In my mind, I know it’ll probably take 30 hours, but I’m going to pad it by 10 hours in case anything goes wrong or there’s a problem or whatever. So I tell you 40 hours. It will magically take 40 hours. So work will expand to fill the time allotted to it. It’s like the day before you go on vacation, you can get a ton of work done because you’re going to be gone for the next week. When you get back from that vacation, though, it takes you all day just to answer a few emails. This work will expand to fill the time allotted to it. So that’s Parkinson’s law. And this affects activity duration. Sometimes it’s called the student syndrome because what happens is I say it’s going to take 40 hours. And I know I’ve packed in 10 hours.

I’ve padded it. Well, the worst thing I could do is wait to hour ten. And now I have 30 hours to get it done. So I hope and pray when I get to hour ten and actually do the work with 30 hours that I don’t have a real problem or a mistake because then it will affect when I complete that task. So Parkinson’s Law student syndrome, we can do voting on how long activities are going to take. So I’m with my project team and we’re doing some predictions here of how long it will take. How confident are you in this estimate? So one approach is called a fist of five. A fist of five, sometimes called a fist of five is if I show my fist, that means I have a zero, zero confidence. That’s a good estimate. If I show a five, that means full support. That I think that’s a great estimate. And you’re spot on. So everybody does this with each activity.

So however many fingers you show, that’s how confident you are as you vote on how long a duration you should take, basically your confidence level. Do you agree with the estimate or not? If anyone shows fewer than three fingers, a two, a one, or a fist, then that person has to speak up and say why they don’t think that is an accurate estimate. And the idea is that it facilitates and it helps encourage the conversation to get people to speak up and to find a good duration for each activity. So know that that’s new in pinbox six. Know that idea of a five to five, you aren’t punching somebody, that just means zero. So what goes into our estimates? So we do our estimates. We do our duration prediction. Here we have a range of plus or minus of days or weeks. So it’s going to take 180 days plus or minus two weeks plus or -14 days, whatever Is Appropriate. You could do a percentage of acceptable target date.

So it will be 180 days plus or -10% you need a basis of your estimate, so it shows how reliable and your confidence level in the estimates you’ve created. So what assumptions and constraints were factored in the range? We just talked about that range of variance. What’s your overall confidence level or your overall comfort level with the final estimate? So if you don’t have a whole lot of information to base this estimate on, you’re probably not too confident. You should also identify any risk that could influence the estimate. Like, if this risk happens, it’s going to cause a pretty big delay in our project. So that risk could threaten not only money, they could threaten our time or duration of our project. All right. Great job. A lot of terms here. I Know. Keep moving forward. I’ll see you in the next lecture.

**Creating an Analogy**

Analogous estimating is one of our tools and techniques to predict the duration of activities. Analogous estimating is creating an analogy between projects, between activities. It’s a way of taking similar project work and saying, OK, that project took six months. Ours is very similar, maybe just a little larger. So I’m going to say it takes nine months.

So it creates an analogy between similar project work. I have to have historical information to do this because I need a similar project to create my analogy on. This is also known as top down estimating because I’m starting at the top and working my way down. An analogous estimate is not very reliable. It’s fast, it’s the least expensive of all of our estimating approaches, but it’s the least reliable because it’s just a quick subjective the historical information is required. I can’t just pick this out of the blue, right? I have to have something to compare it to and they have to be similar. So I can’t take a manufacturing project and create an analogous estimate to an It project.

They are not really similar work. Obviously the historical information also has to be reliable. If that previous project didn’t have its updates to the schedule and activity durations, we may not be based on reliable information. So on paper it says it should take six months, but that project in the past actually took twelve months.

So our analogous estimate would be flawed because we’re not basing it on reliable information. Expert judgment is also used with an analogous estimate because I can look at that project and really understand the work and understand the work of the current project. And then from that I could create a more reliable analogous estimate because I have experience and the expertise to really compare and do some critical thinking between those two projects.

So some very simple examples. Project a took six months. Project B is a little bit bigger, so I predict it will take eight months. So it’s pretty simple, pretty straightforward. So that’s an analogous estimate. You could also do it based on hours. So you could say, all right, it took 8 hours to install this fixture in the past. Well, that was hard to say. You could say it took 8 hours to install this fixture on a past project. But we’ve learned how to install the fixture properly. So we understand the process of installing this fixture. So it should take us about 6 hours now. So we have some learning curve there that we talked about, but we’re also using an analogous estimate. Okay, so that’s an analogous estimate. Know that for your exam.

**Applying Parametric Estimates**

Another estimating approach is called a parametric estimate. A parametric estimate means that we have a parameter for estimating. You use a parametric estimate when we have repetitive work, when we can identify the learning curve. So, examples of a parametric estimate, there’s some type of an algorithm to keep calculate the duration of activities. So a time per unit, so it will take 2 hours to install every fixture. It takes 8 hours to install the garage doors, and you’ve got a bunch of garage doors to install in your condo association. So a time per unit, square footage and again, historical data can help predict this. So you just have some parameter and you multiply it across.

I have 2000 units, 1 hour each, 2000 hours. So it’s a parameter to predict for repetitive information. I can’t do this with tasks that aren’t the same. It’s for repetitive activities. Duration and effort are not the same thing. Duration, we’re talking about how long an activity will take. An effort, we’re talking about billable time for the labor, the effort, the amount of labor you exert to do something for a duration. So here’s an example of effort in duration, we have an activity that’s going to last 40 hours. We have a senior engineer, and we also have a part time person that could also do this task. So, two opposite extremes here. The senior engineer could do this activity in 40 hours.

The cost, though, may be more to pay that senior engineer than what this activity is worth. A part timer, they could do this in two segments of 25 hours. So they’re going to work 25 hours one week, 25 hours the next. So 50 hours total. But the duration is going to be two weeks, right? It’s going to be two weeks until they’re done with that activity at only allowing 25 hours a week on that task. The part timer, though, they’re a much lower rate than what our senior engineer is. So we have to think about a couple of things here. One, how long will that activity take to complete? If the senior engineer does it, the duration will be 40 hours. If a part time employee does it, the duration will be 50 hours, but it will be two weeks, because that resource is also limited to 25 hours a week.

So what’s more important here, time or money? Well, we don’t really know from this scenario, but we may need that activity faster than two weeks. So it would be more cost effective to put the engineer on this activity, and we’re done in five days, 40 hours total. Then it would be to pay less, but it takes two weeks to get done. So duration and effort are linked. And we’ll also see that when it comes to resource rates. In the next chapter, the next section when we talk about cost management. All right, great job. Keep moving forward.

**Creating a Three-Point Estimate**

Another estimating approach that you can use is a three point estimate. And there are a couple of variations of this you’ll need to know for your exam. A three point estimate is where we find the average of the optimistic, the most likely, and the pessimistic. This approach to three point estimating is called a triangular distribution. Distribution because we have a triangle of optimistic, most likely and pessimistic. So there you go, it’s triangle. So in this example, if we had an optimistic estimate of 25 hours or most likely 45 or pessimistic, the worst case is 75. So we took 25 plus 45 plus 75 and then divided by three, it would be 48. 33 hours. So that’s what we would predict, how long that activity would take. Another approach is a pert technique. It’s also a three point estimate. And this is called beta distribution. So it’s a little different. Pert means program evaluation and review technique, but we just call it pert. What pert does is it’s weighted towards the most likely, where the triangular it was just an average. Pert has a little weight or weighted factor for most likely.

So what we’re doing here, we take optimistic plus four times the most likely plus pessimistic divided by six, and that will equal our estimate. So we’ll take the same case here, 25, 45 and 75. So we take four times 45 plus 25 plus 75. And whatever that comes out to be, we divide by six. And then we would say it’s 46. 66 hours we’re weighted, meaning that we’re putting more belief in the most likely time. So this is called a beta distribution. It’s factored towards the middle. It’s a beta distribution, three point estimates. You might also see them abbreviated like this on your exam. Don’t let it worry you, don’t let it throw. You were most likely might be a T in an M, optimistic a T in an O, and pessimistic, a T and a P and then a three point estimate, a T, uppercase E.

And then you can see the little T there preceding all of our factors. The t just means time. So a little hint, you can also do this with cost. So instead of a T, you might see a little C there. And so the C would be it’s a cost with the three point estimate. And we’ll see that in chapter seven. Let’s compare and contrast here. All right, so we have an optimistic of 40 hours, most likely 55 pessimistic of 70. So what happens if we do it with pert? And what will happen if we do it with our three point estimate? So what will the results be? So let’s take a look at our formulas. So our total for the three point estimate, if we take 40 plus 55 plus 90 is 185 divided by 361. 67, that’s our average amount of time. That’s what we would predict if we use pert. It’s 40 plus 55 plus 90.

And then you can see our formula. 40 plus four times 55 plus 90 divided by six. So you sum those up, divide by six, and the answer would be 58. 3. So what’s happening here is with a three point, it’s just the average. So if you have a very negative pessimistic or a really aggressive optimistic estimate, it will skew your average. In per, everything is skewed, if you will, or weighted towards most likely. So you have to have a lot of confidence in your most likely estimate. You do this for every single activity to do three point or pert. The reality is you could take just some of your activities and do this. But for your exam, it’s used through the whole project. So that’s pert and three point estimate. So know how to do those. You’re probably going to have to do that math on your exam. Alright, keep moving forward. I’ll see you in the next lecture.