Another estimating approach that you can use is a three point estimate.
And there are a couple of variations of this she'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 thing approached a three point estimating is called a triangular distribution because we have a
triangle of optimistic most likely and pessimistic.
So there you go 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 divide by three.
It would be forty eight point three three hours.
So that's what we would predict how long that activity would take.
Another approach is a perch technique it's also a three point estimate.
And this is called beta distributions so it's a little different.
Pert means program evaluation and review technique but we just call it what it does.
It's weighted towards the most likely where the trained gular it was just an average person has a little
little weight or weight it 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 or whatever that comes out to be.
We divide by six and then we would say it's forty six point six six 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 a beta of our X factor towards the middle.
Beta distribution.
3. estimates You might also see them abreviated like this on your exam.
Don't let it worry you don't let it throw you where most likely might be a t in an optimistic t and
no I'm pessimistic t it 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 that just means time.
So a little hint.
You can also do this with cost.
So instead of a T you might see a little scene there.
And so the C would be it's a cost with a three point estimate.
And we'll see that in chapter 7.
Let's compare and contrast here.
All right so we have an optimistic of 40 hours most likely 55 pessimistic at 70.
So what happens if we do it with perked.
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 three 61 points
point seven 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 you could see our formula 40 plus four times 55 plus 90 divided by six.
So you see some of those up divide by six.
And the answer would be fifty eight point three.
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 per.
The reality is you could take just some of your activities and do this.
But for your exam it's used to 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.
All right.
Keep moving forward.
I'll see you in the next lecture.