All right, folks.
Welcome back now for
session three of Introduction to Project Management Principles and Practices,
University of California Irvine, and again, I'm Rob Stone.
We're going to talk in this session about Scheduling.
It's another element of Planning.
Schedule is a big piece of the Planning.
What's a Schedule all about?
A Schedule is going to show us the relationship of tasks and
activities in our project.
It's going to show us dependencies, which tasks will lead to other tasks.
And it will also show us which tasks happen before certain tasks along the way.
So it's a dependency if we look at this task and see what comes after this,
it's a predecessor if we say, I'm looking at this task and what happened before.
We're going to talk about an example.
What we're going to talk about is flying to Darwin.
We have a company that's located in Dongara, and we have a potential customer
that calls up and says hey, we need some parts and supplies delivered to Darwin.
And we say well we could do that.
When do you need the parts and supplies delivered?
And our potential customer says well, we need those today at 6:00 in Darwin,
6:00 P.M., this afternoon.
And we said it, well it's almost 1 P.M., right now.
We don't know if we'll be able to do that.
You know,
we're going to have to use airplanes instead of road trains to do this.
And we don't know if there's enough time to get it done.
Let us take a look at some information we have and
then ask you a couple of other questions.
So we take a look at information we have about flight times.
We have past experience over years and years and years.
We have specific past experience related to each one of our pilots and
each one of our airplanes.
We know the planes and the pilots we have avail, available.
[COUGH] We know the planes and the pilots that we have available.
So what we're gonna do is look at our charts and
we find out that it takes an hour and a half to fly from Dongara up to Marble Bar,
some of the parts are in Marble Bar, some of the parts are in Kalgoorlie,
we have to fly to both of those places.
The parts and supplies in Marble Bar, it takes us an hour and a half to get there
and to get from Marble Bar over to Darwin takes another two hours for that route.
Now, if we get the parts out of Kalgoorlie, we have to fly down to
Kalgoorlie that's gonna take an hour and then it's gonna take another three and
a half hours to get from Kalgoorlie up to Darwin.
We take a look at that and say, hm.
I wonder how long it takes to load these parts and supplies.
We ask our potential customer that and they say we will load the parts and
supplies for you.
It will take no longer than half an hour, 30 minutes at the most.
If it takes any longer than that, your company is not responsible for
this project coming in late.
We say well to do our route through Marble Bar then with flight times and
loading parts and supplies it's going to take four hours to do that.
We look at the route through Kalgoorlie and we say, if flight times,
loading parts, and supplies, it's going to take five hours to go all around
through Kalgoorlie and get those parts and supplies and then get off to Darwin.
So now we're gonna look at this and say, can we actually do this project in time?
It's almost 1 o'clock and we need this done by 6 o'clock.
We need to look at two things.
What's sequential and what goes on simultaneously.
Sequential things, we have to go from Dongara to Marble Bar to Darwin.
We can't just jump in the plane in Dongara.
Fly over directly to Darwin and say, okay I'm here.
And then the people in Darwin say, where are the parts and supplies?
They say well I'm here in the plane.
Do you need the parts and supplies too?
Yes, the parts and supplies are the main piece of this.
Oh, okay.
Things have to be in a certain sequence.
It has to be Dongara, Marble Bar, Darwin.
It has to be Dongara, Kalgoorlie, Darwin.
Have to be in a certain sequence.
Can these go on simultaneously?
There's no task dependencies here.
There's no reason they couldn't go on simultaneously, if we have two planes and
two pilots, which we do.
So we can do both these routes at the same time.
We look at this and say, hm, well,
how long does it actually take to do this project?
Now we're going to look at Critical Path and Float Time.
Critical Path through the project.
When you lay out all the strings of tasks that have to be in a certain sequence,
one string of tasks will be longer than all the other strings of tasks.
That's the Critical Path through the project.
Our longest string of sequential tasks through this project is five hours.
This project will take five hours.
So if everything goes just right, just right, everything goes fine,
we take off out of Dongara, we get the parts and supplies Kalgoorlie,
we get to Darwin in five hours, everything's just fine.
Yes, we'll take the project.
Now, we've defined the Critical Path, we figure out where that is at.
Now we look at the other part,
the Marble Bar route, there's an extra hour there, Float Time.
You'll also see that written as slack time.
So what is this Float Time all about?
Float Time is the extra time that's in some of the shorter
strings of tasks because they're not gonna take the whole five hours.
This doesn't take the whole five hours.
It takes only four hours.
There's an extra hour.
Weird things happen with the extra hour.
One of them, we may have somebody in our organization that says, I'm only going
to release materials and people at the last minute when you just need them.
So they're gonna keep our Marble Bar pilot hanging around in the,
in the hangar here polishing up hub caps and wiping down windshields,
and they're not gonna release them until 2 o'clock.
So, they're released at 2 o'clock, there's only four hours left in the project.
Guess what?
Now we have two critical pathways through the project.
The Kalgoorlie route is on it's way it only has five, four hours left to go and
it's going to use all of those.
But, now also, the Marble Bar route only has four hours.
And there's only four hours for that route.
We have two critical paths in the project.
You don't want that unless you have to.
I want everybody starting as early as possible because if something goes
wrong in the project, I hope it's where I have a little bit of extra time.
For example, we start to land in Marble Bar.
Bang, tire blows out.
It's gonna take 45 minutes to put the tire on.
We can't load the parts and supplies while the tire's, tire's being put on.
So now this route is going to take four hours and 45 minutes.
Well, we had to pay for the tire, yes.
Risk will almost always cost you more money on the project because
there's usually extra tasks and sometimes more materials.
Doesn't have to mean your project's going to come in late.
This route now takes four hours and 45 minutes,
our project still comes in just fine.
If the tire blows out, bang in Kalgoorlie.
Now we've got a problem.
We put that tire on, now we have a 5 hour and
45 minute route and the project is going to come in late because of the risk,
so we hope the risk hits us where there is some extra Float Time.
Critical path through the project, there is a definition for that from PMI.
And we also have two ways to talk about Float Time.
One of them, the total Float Time.
In a series of tasks there will be some total Float Time.
So in our route from Dangara to Marble Bar to Darwin, there's an extra hour.
It doesn't mean that there's an extra hour in the route from Dungara to Marble Bar
and another extra hour from Marble Bar to Darwin.
It means that totally those two have an extra hour.
Free Float is what's left over after tasks upstream
have already used up some of the Float Time.
So, if the pilot that goes from Dongara, Marble Bar takes an extra 45 minutes,
there's only an extra 15 minutes left for
that pilot that's gonna go from Marble Bar down to Darwin.
That's the Free Float.
Total Float, how much is across all of these, this whole groups of tasks, and
Free Float what's available for my specific task because
previous tasks have already used up some of that Float Time.
What does a Schedule look like?
It looks like either a Gantt Chart or a Network Diagram.
There are two kinds of pictures we can make for our chart.
Project Diagrams.
Gantt Chart.
Network Diagram.
Critical Path Method.
There are two kinds of Network Diagrams.
There's Activity On Arrow Diagrams.
And Activity On Node Diagrams and you'll hear a thing called Pert Chart.
Pert Chart, program evaluation and review technique.
You never need to know that for anything.
But people want to know what it means, program evaluation and review technique.
Don't bother memorizing that, PERT chart is just fine.
And actually, PERT chart is a term that's used very rarely anymore anyway.
People just simply talk about Network Diagrams.
Critical Path Method, that's another way to look at
some of these Network Diagrams and we'll talk about that right now.
Henry Gantt did his first chart in 1917,
the Gantt Chart, a bar chart across a timeline.
Networks Dia, Diagrams, Network Diagrams then came along.
1959, the end of 1959, an Activity on Arrow diagram, which simply
means that Network Diagrams, when we look at a picture of them here you'll see this.
Network Diagrams have things called nodes, little circles or squares or some
kind of picture or something along the way, and arrows that connect those things.
If you write the information about the project on the arrow,
it's an activity on Arrow Diagram.
If you write it in the little box, the circle on the picture,
whatever it is, then that's an Activity On Node diagram.
A PERT chart was one of the first Activity On Node diagrams.
1959, the end of the year, Dupont came up with Activity On Arrow diagrams.
And 1960, just a few weeks later, right after the first of the year, the Navy and
Booze Allen came up with the Activity on Node diagrams.
And when DuPont came up with Activity on Arrow diagrams, they also realized,
hey there's a thing in there we could call it Critical Path.
Up until 1959, no project had ever had the term Critical Path.
Nobody even knew that it was there.
You'd kinda think that people intuitively knew there was such a thing, but
there was not a term for it, not a way to define it, not a way to calculate it.
Now Critical Path is just blended into every kinda chart we see.
Original Gantt charts look like this.
There were bar charts across a timeline.
That represented finer levels of detail.
So they represented another level down in the WBS.
And people said, well you know,
we could probably get rid of those bars across there.
And we'll just put some little lines, and
just represent those subtasks that are in here.
And then some people said, yeah you know,
we've still got this timeline across the bottom, and things are working fine.
But, you know? I have some other relationships
once in while.
Like I have a relationship between three and six.
The relationship between three and sjx means there is a diagonal line,
I am looking at a timeline across the bottom and now I have to figure out
the angle of that line and try and figure out how much time that represents.
And Dupont says that is just getting silly,
let's just write this on the lines and now it's the end of the year in 1959 and
we have Activity On Arrow diagrams put together by DuPont.
And then right after that a few weeks later, right after the holidays, the Navy
says we don't really like writing it on the line, we wanna write it in the boxes.
So now we have Activity On Node diagrams.
This was a way to schedule projects for
a number of years until computers got back into the picture.
And now computers become readily available to people and
computers seem to draw Gantt Charts more easily than they draw Network Diagrams.
So now in the 80s and 90s, everybody says,
let's go to this brand new thing called a Gantt Chart and let's use that.
That's a great way to schedule a project.
Gantt Charts look like this.
Computers draw these better, so this is typically what we see now.
Project schedule, tasks across a timeline,
it's a roadmap for the entire project, for everybody involved in the project.
It's a great communication tool, and it's a tracking tool.
To track your project,
you have to know where you should be today with progress and spending.
And then you track that against where you actually are.
So we have to have a schedule to figure where we're at with the progress and
the project.