Activity network diagram || Critical Path Method || Efficient Project scheduling using an example

hello and Krishna Murthy famille in this video we are going to learn a quality management tool called activity network diagram whenever we are asked to develop project schedule we wanted to have complete knowledge about various attributes of project activities involved that means how the project activities are interconnected with each other what is the early start time early finish time late start time and late finish time of each of the activities involved within the project what is the critical path of the project and what is the product duration it takes to complete the project and also how much time an activity can be delayed so that the end project end date is not impacted what is the amount of time an activity can be delayed so that its succeeding activities start time is not impacted all this kind of activity attributes we need to have then only we can arrive at efficient project schedule using activity network diagram we can achieve this purpose activity network diagram can be represented either by activity on arrow method or activity on node method we use activity or node method in this video to represent the activity network diagram the activity network diagram is also called critical path method let us understand the activity network diagram in detail using activity network diagram we can calculate early start early finish late start and late finish of an activity let us understand these terms using an example now in our example let us take an activity called commute to office by an employee so an employee takes 1 hour to reach his office from his home so the activity name is commute to office the duration is one hour let us say an employee can start at the earliest at his home by 8:30 a.m. so early start is 8:30 a.m. so to get early finish we have to add duration too early start so yearly start 8:30 a.m. plus 1 hour is early finish so early finish is the earliest time an employee can reach office is 9:30 a.m. that is earliest finish so it can be obtained by the formula early finish is equal to early start restoration let us suppose that the employee must be there in office by 10:00 a.m. so the late finish of this activity is 10:00 a.m. so the activity must finish at the greatest or latest by 10:00 a.m. now to get late start that means the greatest time or the latest time an employee can start at home is 9:00 a.m. how you obtain late finish - duration that means late star is equal to late finish - duration so using this kind of thinking pattern we arrive at early start early finish late start and late finish the formula is early finish is equal to early start test duration that means early start plus duration is early finish late finish - duration is late start so using this formula we can obtain early finish early start late start and late finish of an activity let us draw an activity network diagram using an example our example consists of building two new features to the already existing feature set of our product now as part of this we will be performing requirement analysis will be performing design building function testing of these features and then we will be doing integration of these features to the already existing feature set and then we will perform regression testing to ensure that already existing features are not disturbed and their performing in the intended way and then we will deploy and release these new feature set along with the existing features of the product to the market we are asked to draw activity network diagram by giving the details provided here the DVD description requirement analysis is represented by activity a design for feature one is represented by activity B design for feature two is represented by activity B build and the functional test for feature one is represented by C build and a functional test for feature two is represented by e integration testing is represented by AI regression and release activity is represented by our now we will learn what the predecessor means in following slide the duration for each of the activities are listed in this particular column that means activity a takes five days at two TB takes six days likewise the duration is listed in this particular column let us draw a rough draft of activity flow from the details provided here activity a has no predecessor that means there is no activity that comes before an activity a that's how activity a comes as the beginning activity for the activity B and activity D at two T a is the predecessor that means for both activity B and activity D activity a comes before this is how it is represented in the activity snow diagram now for the activity C activity B is the predecessor for the activity e activity D is the predecessor for the activity I acted TC and activity E or the predecessors similarly for the activity our activity I is the predecessor no a clue is an activity that has no predecessor is the beginning activity an activity that is predecessor to no other activity for example if you see our R is not featuring in the predecessor set that's how our is the ending activity so this is how we can draw a rough draft of activity flow diagram if you apply activity description for these activities it looks like this it shows a beautiful meaning it says that requirement analysis is performed for both the features first then designing and building and functional testing of feature 1 designing and building and functional testing of feature 2 are carried out in parallel and they both are integrated here and then finally regression and release is performed so using activity flow diagram we know what is performed first what is performed next what activities are performed in sequential way what activities are performed in parallel way for example BC activities are performed in parallel to D and E so this is how our activity network diagram is looking like this let us calculate early start and early finish for various activities in our activity flow diagram now all the activities in our activity flow diagram are tied up with finish to start relationship for the activity a it can get started at the end of 0 at today that's why early start is zero and duration is 5 so if you add duration 5 to its early start it becomes early finished zero plus five is equal to five so the early finish for the activity a is 5 now this early finish will get carry forward as early start for activity B because activity a and activity B or tied up with finish to start relationship in similar way activity a and activity D are tied up with finish to start relationship so the early finish of activity a will get carry forward as early start for activity D so the early start for activity D is fine so if you add duration 5 plus 6 is equal to 11 so early finish of activity B is level similarly 5 plus 4 is equal to 9 so the early finish for activity D is 9 now the early finish of activity B will carry forward as early start for activity C because they are tied up with finish to start relationship so similarly the early finish of activity B will carry forward as early start for activity E now if you add duration for C 14 plus 11 becomes twenty-five that is the early finish of active PC six plus nine is equal to 15 so that is what is early finish for activity II now look at the blue T here from here you are getting 25 as early start for I from here you are getting 15 as the early start for activity I so what we should take we should take Maxima in forward pass why because activity C and activity I or I'd up with finish to start relationship similarly act to de and active T I or tied up with finish to start relationship so for the activity I to get started both C and E must first be finished so it has to take 25 because even though the activity II is getting finished at the end of 15 days the activity I has to wait till end of 25 because it has to require C to get completed so because activity B C need to be completed the activity I has to wait for this flow that's why we will take Maxima in forward pass so one from one side you are getting 15 from another side you are getting 25 so out of 15 and 25 the Maxima is 25 so we will take 25 as the early start for activity I know if you add 5 to 25 that means duration to early start of a tutti I you will get early finish as 30 now this 30 will get carry forward as early start for activity are because activity I and activity are are tied up with finish to start relationship now if you add file to its early start 30 plus Phi becomes 35 right so this is how we calculate early start and early finish for our activity flow diagram for various activities let us calculate late start and late finish for various activities in our example the late finish for activity R is 35 which is equivalent to the early finish of activity art because of maximum duration here now using the formula late stop is equal to late finish - duration that means we must deduct the duration from the late finish to get lately start so 35 minus 5 is 30 so 30 is the late start for activity are again in the backward pass this 30 will get carried forward as late finish for the preceding activity because they are connected with finish to start relationship so the late finish of activity I becomes the late start of activity are so this 30 is getting carried forward here in backward pass now if you detect the duration from 30 25 so 25 is the late start for activity I this 25 will get carried forward to activity C and activity E as the late finish so if you deduct duration from the respect to late finish that means for at UTC 25 minus 14 becomes 11 this 11 is late start for activity C similarly 25 minus 6 which becomes 19 this is the late start for activity e now this 11 will get carried forward here in backward pass so this is the late finish for activity B and 19 is the late finish for activity D now if you deduct duration that means 11 minus 6 is 5 for activity B this 5 is late start for activity B 19 minus 4 15 15 is late start for activity D now this 5 will get carried forward here and from here 15 will get carried forward here so 5 is getting carried forward here in backward pass 15 is getting carried forward in backward pass which one to take now in backward pass we must take minima because activities are collected with finish to start relationship so out of 5 and 15 5 is minimum so Phi becomes the late finish for activity a now if you did a curation Phi from the late finish you will get the late start for activity a so you got the late finish in backward pass using the formula late start is equal to late finish - duration we now have the early start early finish lates made finish using this representation for all the activities using the formula yearly finish is equal to early start plus duration late start is equal to late finish - duration we are calculating early start and early finish using forward pass and we are calculating late finish and late start using a backward pass let us understand how to calculate critical path and project duration for our example now using the representation he early start early finish late start late finish for an activity we have all these attributes listed for the activities mentioned here now in our activity network flow diagram we have two paths one is path 1 a B C I and our another is path to a B II I and our the total duration of path 1 is 5 plus 6 plus 14 plus 5 plus 5 which becomes 35 days the total duration for path 2 is 5 plus 4 plus 6 plus 5 plus 5 which becomes 25 the critical path is the longest path in scheduled network diagram so the critical path is a B C I and R so the activities colored in maroon color or critical path activities so the critical path duration is 35 days so if anybody asks us how much time this project takes I will say minimum 35 days I need why because 35 days is the critical path duration so minimum 35 days I need to complete this project so critical path is the minimum duration a project takes to finish so from critical path we arrive at project duration any delay to the activities on the critical path will further delay the project duration so that's why we do not have any float on critical path remember I use the term float float of an activity or total of an activity or one and the same they both are synonyms so afloat of an activity is the amount of time an activity can be delayed without impacting the overall project end date it can be obtained by either of the formulas late start - early start late finish - yearly finish if you apply this formula for any of the critical path activities you will find the total float or float as zero for critical path activities this is obvious because we cannot delay the critical path activities any delay we do to the critical path activities will delay the overall project end date that's why usually the critical path activities will be having zero float in advanced project scheduling you may find a situation wherein it can be negative but that is beyond the scope of this lecture usually the total float of critical path activities are zero when it comes to non-critical path activities okay you will find certain float by applying the same formula late start - early start for an activity D a as 10 so 15 minus 5 is 10 so that means the activity B can be delayed up to 10 days so the project management can consider incurring glaze up to 10 days so that the project overall end date is not impacted so that's the beauty of the float so similarly for the activity e also we have the float as 10 late finish - early finish 25-15 as 10 so activity e can also be delayed up to 10 days under special circumstances so if we incur delay more than 10 days then the critical path will change because the project end date is changing and the critical path will change from ABC I R to a de I R so we cannot have delay more than 10 days on this path so that's beauty of knowing the term float for an activity there is another term called free float of an activity free float of an activity is the amount of time in activity can be delayed without impacting the earliest start date of any of its succeeding activities if you take activity a the free float of an activity a is amount of time activity a can be delayed without impacting any of its succeeding started early start date of activities that means the early start date of activity B and early start date of activity D or the succeeding activities of activity a so how much time I can delay zero because the the activity a is finishing on v B and activity B and activity D must start on v day so the free float is zero obviously the free float of activities on the critical path is always zero because we cannot delay critical path activities but when it comes to the free float of activity II if you see here the free float is 10 because the activity II is finishing at the end of 15 today and even if i delay by 10 days its succeeding activity I is not compacted because the succeeding activity I is starting at the end of 55th day so 25 minus 15 is 10 so 10 is the free float of activity II the difference between free float and total float is in free float we are measuring activity with respect to the early start date of the succeeding activities whereas in total float when we consider total float of an activity we are concerned about total project end date that's the difference the terms free float and total float gives you the scheduling flexibility available in the activity Network diagram thus activity network diagrams helps in efficient project scheduling of a project or process activities through determining precedence and succeeding activities sequential or parallel order or sequence of activities early start early finish late start and late finish for an activity critical path and project duration free float and total float for an activity the amount of scheduling flexibility available thus not only arriving at efficient project scheduling this activity network diagram also helps in identifying scheduled risks within the project or process activities involved I thank your interest to learn and I look forward to add more value add sessions in future thank you

Channel: Krishnamurty Pammi

Views: 3,019

Rating: 4.7931032 out of 5

Keywords: Activity network diagram, Critical Path Method, Project scheduling, PMP, Quality Management, Quality, Schedule Management, Time Management

Id: ij2Bmp6YMEE

Length: 21min 10sec (1270 seconds)

Published: Sat Oct 27 2018