hello and welcome to this video guys
today
in this video i will be helping you out
with one of the tricky concepts
in the context of project network
diagram lead and lag
questions from this topic in your pmp or
capm
exam are generally of a high difficulty
level
so make sure you pay full attention
throughout this video to understand this
concept very thoroughly i guarantee that
after watching today's video you will
never face any difficulty in
understanding the concept of lead and
lag
or answering any type of questions from
this topic in fact at the end of this
video we will be solving a tricky
question
from this topic like your actual pmp and
capm exam
so let's get started firstly you need to
know that the terms
lead and lag are very different from the
terms slack and float
now if you have any query or any doubt
in understanding the terms
slack and float with respect to project
network diagram
i suggest that you watch this video
right here on critical path method
because i have explained the terms slack
and float
in great detail in that video but in
today's video we'll be focusing only on
the terms
lead and lag in context of project
network diagrams so what are we waiting
for
let's jump to my whiteboard and let's
get started okay so we will start first
with understanding the definition
of what is lag so let's see what pmbok
says about lag
so the definition of pmbok for lag is a
lag
is the amount of time or successor
activity will be delayed
with respect to a predecessor activity
okay
now if you see there is this term will
be delayed okay here so it means that
there is a mandatory delay which is
associated with the definition of lag
okay now to understand the definition of
lag much better let's take an
example so you are the construction
manager of a site
and you are building for example let's
say a
concrete beam and you have to build a
wall
over that concrete beam okay now if we
define the activities for these
activity one is lay concrete for the
beam and activity two is
build the wall on the beam after that
activity so activity one
is the first activity and activity two
is the
successor activity now if you try to
understand the dependency of these two
activities
from a practical scenario you will see
that
there is a mandatory weight of 21 days
between these two activities
so generally what happens is when you
lay down the concrete for a beam
you have to wait for 21 days to let the
concrete cure and become hardened so
that
when you start building the wall over
the beam the concrete or the beam
doesn't collapse okay
so it depends on the type of concrete as
well so generally it is somewhere
between 14 to 21 days
so irrespective of what the days may be
there is a mandatory weight
of some time between activity one and
activity two
okay and that is what is called a lag
so if you try to understand or try to
remember the definition of lag
as i define it i define it as
a mandatory waiting time between two
activities
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in future now since we have understood
the concept of lag
let's try to understand the concept of
lead so if you see the pmbok definition
of lead
it is the amount of time a successor
activity can be advanced
with respect to a predecessor activity
now this can get a bit tricky guys
so let's try to understand it with an
example
say for example in activity 1 you have
the delivery of books
from amazon some of the books which you
have ordered and in activity 2
you go ahead and complete reading all
the books okay
let's take this example now if we
associate some timelines to it
let's say that from 1st to 5th of may
the books will be delivered
in 5 days and you will start reading the
books after that which is from 6th may
and you will take about 21 days to
complete reading all the three books
which is
26 may so the full project if you say
it's a mini project completes in 21 days
plus 5 days which is 26 days right
now let's try to understand another
scenario of
this project where you order the books
from amazon for sure
but instead of waiting for the books to
arrive you start reading the preview
pages of the books
from the kindle store let's say for
example okay
so that at least when the books arrive
you have already read some pages of the
books
as the pdf copies or the soft copies
from the kindle
store so that way what you are doing is
you are pulling forward
your activity to buy some days let's say
for example
four days now if you try to associate
some timelines to it
your initial activity one will always
take five days the hard copy of the
books will always takes five days to
arrive
but what you can do is instead of
waiting you can start reading the
preview pages from the kindle store
and you can start reading them maybe
just after the day when you order
the books right so you can start reading
the books on second of may considering
that you have placed the order on
first of may so that way what you are
doing is guys you are pulling forward
the next activity by
approximately or in this example by four
days
right so that way your project initially
when it was to complete on 26th of may
now gets reduced and it will be
completed on
22nd may and that is because for the
initial four days
you will read the books from kindle and
once the books arrives on the 5th of may
you will start reading the other pages
of the book okay
this concept where you actually pull
forward your successor activity by some
days
to actually give you some advantages in
schedule is called
lead now if you try to understand lead
as the way i remember it it is the
opportunity to pull forward
your next activity okay next
let's try to understand how lead and lag
is represented in network diagrams
okay now if you see our first example of
concrete and
wall we had a mandatory lead of 21 days
between the two activities right
now if you try to represent it in a
network diagram it is activity 1
lay concrete beam and activity 2 build
the wall on the beam
now these two activities guys has a
finish to start relationship
that is the construction of the beam
should be complete
before the wall can be started to build
on it and between these two activities
you have a lag of 21 days
so here is how you represent lag in
network diagrams
it is with a plus sign okay with the
number of days
so here it is finish to start plus 21
days
so that is meant by lag now if you see
another important thing here guys
there is no overlap between activity one
and activity two right so there is a gap
which you see here and that is why it is
also true that
first thing these two activities are
finished to start
and second thing there is a lag between
these two activities so that is how you
represent lag
in the network diagram now an important
takeaway for lag
guys which you need to remember which is
very important is
lag is also possible on other types of
dependencies such as start to start
start to finish
or finish to finish right so in totality
lag can be applied to all the four types
of dependencies
which is mentioned in pmbok with that
let's try to understand
how lead is represented in network
diagrams
now if you remember our example we had
ordered some books on amazon but before
the books arrived we started reading the
books
through kindle the preview copies and
that way we actually pulled forward our
next activity by 4 days
so if you see here activity 1 was
delivering the books from the amazon and
activity 2 was
start reading all the books and start
with the preview pages
in kindle now this was also a finish to
start relationship guys
that you had to have the books getting
delivered so that you can
start reading the books right you can't
read the books without the books
having physically arrived right so that
way it's a finish to start relationship
now how do we say it's minus four days
because it's a lead
that is why it is negative in the
network diagram so always
remember that since lead always helps
you in your schedule it is represented
by a negative sign so
you are gaining on your schedule and lag
since it
actually adds up to your schedule it is
represented by a positive sign
so that way you are adding on days into
your schedule so try to remember like
that it will be quite easy
now if you see here another important
thing there is a bit of overlap between
the two activities right which you do
not see in the lag definition right
and that is why the concept of lead is a
bit tricky to understand because
lead is applicable to a finish to start
relationship and there is always some
overlap
in the gantt chart between the two
activities so here
there is a overlap of approximately four
days for this example
okay now here is a word of caution guys
if you're reading the
lead and lag definition from pmbok be
very careful that there is a typing
mistake here
where pmbok is explaining the lag
definition through the diagram
here you will see that it is negative
but it should not be negative so
whenever you define
lag even if it is a start to start
relationship it should always be a
positive sign so as we
learned that lag is always positive in a
network diagram so be very careful with
it
else everything is correct here just
with respect to this definition
please note that there is a typing
mister here this should be a positive
sign not a negative sign for lag
now two important things which you need
to remember for lead
is number one lead cannot happen for
mandatory dependency
okay now let me take a minute and
explain what this is if you see these
two activities
it was not mandatory that you have to
wait for five days
for the books to arrive so that you can
actually read the books when they write
physically right you had the option to
start reading the preview copies through
kindle right
now that way you had an option here but
what if these books didn't have a kindle
copy right
and that way you would have been left
with no other chance but to wait till
the books arrived and then you have to
start reading the books right
that way this dependency would have
become a mandatory dependency
and that way you could not have applied
the concept of lead in this example but
here
since the books had a kindle copy where
you can actually start reading the books
before even they arrived
and that is why you need to remember
that lead cannot happen for mandatory
dependency it should only be
discretionary dependencies
of activities when you apply the concept
of lead
now the next important thing and it's
very important guys which you need to
remember is
lead is only applicable for a finish to
start relationship
if you see in lag it is applicable for
all the four types of dependencies in
the pmbok
lead is only applicable for finish to
start relationship
and lead is represented by a negative
sign lag
is represented by a positive sign so
these
are the most important takeaways from a
network diagram standpoint for the
concepts of
lead and lag i hope this concept is now
much clearer to you than it was before
let's test that out by solving a
question just like the actual pmp exam
in our next slide okay so we will move
on to a question of lead and lag
and let's try to answer this question
with all the concepts that we have
understood till now
the question guys pause the video try to
answer the question before moving
forward okay
so let's start by understanding the
question a software development team can
begin to write
okay notice the word here begin to write
the scope of development only after two
months of start of design
okay this is to ensure that the team has
sufficient data points from design for
writing the scope
what kind of dependency this would
represent okay
now if you see here the development team
is asking for something
from the design team to start the
development work right so the design
team has started the design but
only after two months there will be some
data points which will be generated
so that the development team can start
writing the scope
now if you see the type of dependency
here it is a start to start dependency
that you start the design
but you have to wait for two months so
there is a mandatory wait of two months
before you can start writing the scope
so it's a start to start dependency
with a two month of lag and there is
this condition of
mandatory weight as well that is the
scope writing activity cannot start
till two months the design activity has
started so the correct answer is
option a which is start to start plus
two months
and as we learned that plus means a lag
so it is a
lag of two months so if you see here
guys we see another example of
lag here which is with a start to start
relationship
if you remember the previous slide we
discussed right that lag is also
possible on
start to start start to finish or finish
to finish relationship here in this
example we saw the lag in terms of a
finish to start relationship but here in
this question we saw
the example of lag from a start to start
relationship
as well so the correct answer is option
a which is start to start plus
two months of lag i hope today's video
was useful
and now you are more confident in
solving questions
from the topic lead and lag in your pmp
or capm
exam if you still have any doubts on the
topic lead and lag make sure you drop a
comment in the comment section below and
i will try to help you out with that
okay so thank you for watching today's
video and i'll see you again
in another video like this bye