Project Scheduling 2 -Calculating variance and probabilities -PERT/CPM

Project Scheduling 1 -Finding Critical Path video: • Project Scheduling - P...
This video shows how to
• Calculate expected times
• Calculate variances
• Calculate probability of completion of project at specified time
• Calculate the project completion time given probability
00:00 Intro
00:34 Calculate Expected Time (t)
01:39 Calculate Variance
02:32 Calculate Probabilities
03:33 Calculate t given probability

[@Osorio]

Watched 4 of your videos, learned my whole semester

[@safaerizki7345]

LMAO Same here

[@giannistsagarakis3187]

the guy is unbelievably efficient

[@yangteo803]

Which 4

[@katiabarretto1802]

i learned more from this 4min video than i did in my 2 hour class. thank you

[@rt2000rt]

Thank you sir, you just summarize my 2 hours course into 4 minutes. Well done sir.

[@pagalhokya]

My degree might as well have "The University of Joshua Emmanuel" written on it. I pretty much learned my MBA concepts from you. You're better than most professors out there.

[@pardonfox331]

God Bless you Josh, you are indeed living for others. You are a Super Instructor..

[@deeptikumarroy8630]

This is a summary of an hour long lecture. Thank you so much!

[@bakihanma1680]

holly shit, you just saved my ass bro, my final's on monday & idk tf that even was when my prof explained it, and you did it in 4 minutes & I understood it all so easily. god bless you.

[@deepthivanasarla1762]

Thank you so much. You are just like a god. explained so detailed.

[@mave4395]

Thank you for making the video! Now I know what Scheduling of project is all about

[@ganee]

This video is valuable even after 5 years. This video made me understand what my lecturer couldn't.

[@joshemman]

Glad to hear Ganee. Thanks for dropping a note.

[@rifat115]

Same to me❤

[@rifat115]

​@@joshemman thanks for the videos ❤

[@ronaphiri2814]

Really educative in such a short period of time thank you🙏🏽

[@alejandramarentes6377]

best video ever, you solved all my doubts!! thank you so much btw im from Monterrey Mexico

[@keremt.c2384]

Thanks to you, I passed my final exam. Thank you so much.

[@quratulaind3168]

I wish i found you during my bachelors in engineering, I would have made a far confident engineer

[@bogsespelekpek6542]

This is exactly what i am looking for! Great presentation! Keep making video to help others like me, who is trying to figure out what is missing on my book 🤣🤣🤣 youtube is really a great help to students! Thank you so much!

[@camilaparola2781]

Great explanation! Thank you!

[@SA-ty5du]

Excellent videos , thank you so much 🙏🏻

[@turkialbarakati2022]

Really very great. This video helped me a lot !! Thanks..

[@nicgaddin3889]

This dude is the best on KZbin!!! Da General

[@glomari62]

Have got an exam and this has really helped! Thank you!!

[@jiamiamom]

test coming up April 10. THANK YOU SO VERY MUCH

[@MrAbiteha]

Superb. Short and precise.

[@justinhall7022]

You are a lifesaver!

[@bensmith6987]

Great video. Thank you.

[@michaelmanias4560]

Thank you for making this!

[@elliotbrush6854]

Great video - very informative and easily digestible!

[@joshemman]

Thanks, Elliot. Nice to hear.

[@TheNeighborhoodCat]

this shows you that there are much more effective methods of teaching.

[@natalieinspired8]

You deserve a medal.

[@texculp67]

I stand AMAZED! Concise and presented professionally!! I want to work with you!!

[@joshemman]

Thanks for the comments, Tex. Want to work with me? I'm honored.

[@WillisMadden]

Great Instruction!!!!!

[@belindagonzalez866]

You are awsome, your PPT was great it was perfect.

[@roseannrawls1584]

This was Perfect...

[@jhozellexxsz2624]

thank you so much, sir!

[@saribshakeel8767]

Thank you for clear and precise understanding on this topic

[@joshemman]

You're welcome, Sarib.

[@vrushali9599]

Thank You For this Amazing video...👍👍

[@hashemalkhatib5543]

Hello Joshua , Thanks for clear explanation . please which program are you using to present your videos ?

[@Lydie97]

best explanation!

[@preritgoyal9293]

Very nice video sir. Short and sweet 😊😊

[@isha6289]

Thank you so much❤

[@Sabrina-lo9vq]

thank u for saving me !!!

[@sawmtea5755]

So helpful!

[@aaryanbudhiraja1656]

lol transformed an hour's lecture into 10 minutes, hats off

[@drunkengunner9092]

I love you man. Thank You so much.

[@drunkengunner9092]

from Indian Institute of Management Amritsar.

[@varunbahirwani333]

Superbbb content 😃😃😃

[@MaxTheKing289]

Thanks for this... A whole semester in 4min

[@joshemman]

Happy to help!

[@ahmedibrahim4542]

thanks alot It really helped me

[@pushpavechalapu6579]

Super sir ,I understand clearly 👌👌

[@Olivia-light.joy.and_peace]

big brain :) thank you!!

[@moseschikusela9182]

You are great

[@bestxboxclips4331]

I have an exam tomorrow, I love you, thanks so much

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same as me i love him so much he is my hero

[@patrickbelasa5987]

nice!👍

[@kiranpannu3822]

from where we get optimistic,most likely and pessimistic values?

[@WonderlandX-fc3ss]

If there are 2 critical path, which one should we use to calculate variance?

[@KingK742]

Wa khasta monna 🫡

[@husseinahmed4348]

Astonishing ....could u teach us project crash

[@chandrashekharneupane2464]

Thanks maan

[@Anonymous-mi6]

What is the probability that the project will need or take more than 31 days?

[@aissajez911]

3:55 I think there's an error there when you said the project should start 36 weeks earlier, I think the project should start 3.7 weeks earlier than the initial planning to end on time with 90% probability, because what we have calculated is the total duration of the project (critical path) and it's 35.7w, while we had 32w as initial duration. so we should substract 35.7-32=3.7weeks. not about 36 weeks earlier. correct me if I'm wrong please

[@otanifederio4989]

where do u ge or how do u get m(6)most likely and b(14)pessimistic

[@joshemman]

For academic purposes, they (a, m, b) will be provided for you. But practically, you know from records or experience on past projects.

[@zenapsgas]

There are different ways to calculating the variance. My book says variance = (t-a)/(b-t) / 7

[@diavionnewilson6789]

How would I go about calculating probability of completion time of, for example, exactly 37 weeks. Would I be able to answer less than or equal to 37 weeks and this would be sufficient? Or do I need to subtract probably of more than 36 weeks but less than 38 weeks?

[@joshemman]

The probability of "exactly" should be zero because we're dealing with a continuous distribution.

[@cleanenergy79]

How did you get 32 as the mean

[@shizuchuan]

Hi, how did you get the values from optimistic to pessimistic? Thank you

[@joshemman]

Let's just say they are already given to you.

[@markjoons]

How can we get it from the given first value

[@phonugper7880]

Hi Joshua, may i know what software you use to animate the chart?

[@joshemman]

I use PowerPoint for the charts but I edit and annotate using Camtasia Studio.

[@themage5175]

If there are multiple critical path, does that mean we need to find probability for each path?

[@joshemman]

Typically, you use the critical path with the largest variance.

[@woweffect9731]

Hey Joshua nice video, one question: what if the Time t is not an integer...? Round it up...?

[@joshemman]

Time does not have to be an integer. So only round if necessary or required.

[@chriskerley1508]

Why is the normal distribution used?

[@frankdavidpascual9777]

You save my job dude! Aahahah

[@ZoePaal]

Helpful, thanks. Do you have a Google Sheet template to do this or can you recommend one?

[@joshemman]

You mean, to calculate the normal probabilities?

[@ZoePaal]

@@joshemman Thx for the reply. The whole thing actually. From the table for calculating variance to calculating those z scores

[@ender_paul]

Can you find the critical path if the only given is optimistic, most likely , and pessimistic?

[@joshemman]

You must know the predecessors as well.

[@maddieisntreal8351]

what should i do if the expected time is NOT an integer? thanks

[@joshemman]

Nothing differently. It just makes calculations more challenging.

[@gilangtjahyadi826]

sir i have one question, at 2:47 u got the value of P = 0,8508 from the table, how u get that value? and what the table is that? i don't understand, would u like to explain me please... thank you.

[@joshemman]

It is the Z-table (the standard normal table). You can find them online if you do a simple Google search.

[@gloriasheen6336]

why do you use standard deviation? when do you not use it?

[@geraldobakhume3904]

SD is used to calculate the probability. The Z formula.

[@bmtamim7818]

Why (a+4m+b)/6? Is the 6 is fixed or this can be changed?

[@joshemman]

The 6 is fixed. It's a weighted average. The weights are a: 1 m: 4 b: 1 Total: 6

[@bmtamim7818]

@@joshemman Thanks a lot❤️

[@emilyveneranda6793]

thanks like

[@shresthai3515]

Hi Joshua, Is there a reason why are we dividing by 6? It is always 6 no matter the number of activities?

[@joshemman]

Yes. We always divide by 6 no matter the number of activities. The expected value is a weighted average. “a” has a weight of 1 “m” has a weight of 4 “b” has a weight of 1. Total weight = 1 + 4 + 1 = 6

[@shresthai3515]

Oh thank you very much. @@joshemman

[@andrewmurschel2608]

I had this same question. Glad it was already answered :)

[@AkinveNazIrlanda]

Importantly, if 36 weeks promises %90 chance success of the project, is that mean 32 weeks promise %80 chance of success?

[@joshemman]

32 is the mean. It promises 50% chance of success.

[@AkinveNazIrlanda]

​@@joshemman Okay. Can we use this technique in also construction sector for activity and project estimations? Some people says it is not convenient because of %50 chance. Let say, still we choose this technique for application. What would be the good part to use PERT in that field? Thanks.

[@skylarkenneth2407]

@@AkinveNazIrlanda PERT can be used in a construction setting, that's what I inferred from reading my textbook. PERT originated from the military with unknown duration of tasks to be completed in a research and development environment. PERT was designed for uncertainties. However, using historical data or logic to construct reasonable time estimates for task duration is a big plus. If you look at the stats in the video, 4 more weeks for +40% success rate...seems worth the wait.

[@jieben777]

How did you compute for the area???

[@joshemman]

It was obtained from the Z table.

[@rei-fg1kk]

Hi, how do you get the z score of 90%?

[@rahults1064]

in the table we need to check which value has .90 In table .8997 was close to .90 so we take z as 1.28

[@rei-fg1kk]

@@rahults1064 thank you

[@divyanshuraj1356]

How do we find the area for a certain value of z

[@joshemman]

See if this helps: kzbin.info/www/bejne/ppCucqOgpd51fqc

[@boddapaatideepak1624]

Can anyone please say how to a,m and b from the forward and backward diagram

[@joshemman]

a, m, and b must be given to you. You cannot find them from the nework diagram.

[@loggiedude9188]

How did you get the mean of 32?

[@joshemman]

By adding up the expected time for critical activities.

[@olo1135]

at 3:01 how did you find the .3632

[@studytimewithjency]

www.math.arizona.edu/~rsims/ma464/standardnormaltable.pdf

[@kennethkayeramos2858]

Hello, what if we want a 99.99% probability of completing the project on time, when we should begin?

[@joshemman]

You can use your table or use =NORMSINV(0.9999) in Excel. This will return a Z score of approximately 3.72.

[@kennethkayeramos2858]

@@joshemman I'm confused sir, why dont we use the 3.69 and also the 3.70, 3.71, or either 3.73. They all have the same

[@joshemman]

@@kennethkayeramos2858 Are you using table or software?

[@kennethkayeramos2858]

@@joshemman table, sir.

[@yasserbaroudy5275]

Where can I find the z chart?

[@joshemman]

Just Google "Z table"

[@aricleekirsten724]

How did you find the mean of 32?

[@joshemman]

The mean is found by adding up the Expected Times for critical activities.

[@aricleekirsten724]

@@joshemman Thank you sir!

[@ammarelmazi8370]

Is it always divided by 6 ?

[@joshemman]

Yes!

[@kotagyan3702]

Most uncertain activities is which one????

[@joshemman]

The one with the largest variance (or range).

[@marianna3876]

Sir, I'm a Vietnamese student. Can you explain to me why there is 0.8508? 2:46

[@joshemman]

You can use the z-table (1.0 under 0.04) as shown in 2:46. Or you can use Google Sheets =NORM.S.DIST(1.04).

[@marianna3876]

@@joshemman thank you. Appreciate your help ^_^

[@lesbournericketts6021]

Any utech student here?

[@nanzangusililo6844]

Still lost

[@joshemman]

Where are you heading for exactly?

[@bogsespelekpek6542]

This is exactly what i am looking for! Great presentation! Keep making video to help others like me, who is trying to figure out what is missing on my book 🤣🤣🤣 youtube is really a great help to students! Thank you so much!