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Thank you!

I've been meaning to create the accompanying math videos (in which I'll develop the math from scratch for each video) but haven't had the time yet. It's still on my to-do list.

You're welcome!

Thank you so much for your kind words! I'm happy to hear the video was useful!

Correct. The stage-1 solution needs to be aware, a priori, of the possible scenarios of stage 2 and their respective probabilities. If there's a potential "other" scenario with a non-zero chance of taking place, you could include that too at the beginning and estimate some data for it.

The flow constraints ensure that supply departs from the supplier notes (1 and 2) and that what happens at intermediate notes makes logical sense: whatever goes in has to go out. It also ensures that the demand nodes receive what they need.

Thanks! And you're welcome!

Thanks! Here's a book I like on these topics (at around a senior undergraduate/MBA level): "Spreadsheet Modeling and Decision Analysis" by Cliff Ragsdale.

Thank you! I do have many video ideas for both basic and advanced topics. The hard part has been finding time to make them.

Thank you for the feedback! If you still want more practice with sensitivity, I have a third video on this topic here in the channel as well.

You're correct. The problem in the video is, like every model, a simplification of the real-life situation. As you explain, there are many other factors that need to be taken into account. For the sake of a student learning these things for the first time, we could start with the model presented here and, little by little, incorporate additional details and increase the complexity. Depending on the needs of the transportation company, the level of complexity can reach a point where optimization can't handle it anymore and we need to resort to so-called heuristic approaches (a topic that I don't yet cover in my videos, but hope to get into at some point). I have a few friends who work as research scientists at Amazon and they tell me that this is indeed the case.

Haha! You are too kind! Thank you!

From the description you provided, it sounds like you can!

@@TallysYunes - but how do I compare between different stochastic scenarios?

I'm not sure what you mean by "compare between different scenarios."

Oh my! This is so great to hear! Thank you!

You're welcome! Glad to hear that the video helped!

It's not clear to me what's happening in your case. What do you mean by "displaying the same error?" What error is it? Is there an error message?

Yes it's like solver encountered an error in the objective cell

That sounds like a different kind of problem. It's probably a typo in that particular formula (in the cell that is set to be the objective cell).

But I have done everything correct and it's in my mates mac too. Only in mac but.....

You're welcome! Glad to hear it was helpful.

Thanks!

Excellent!

Thank you!

Glad to hear the video was helpful!

Happy to help!

Assuming it was solving before (with 50,000) as the initial amount and not complaining of non-linearity, simply changing the initial 50K to 100K should not be generating this issue. Therefore, it's some sort of bug. I've seen these before with Solver. Sometimes, clicking (or un-clicking) the box that says "Automatic scaling" in the Solver options takes care of this.

@@TallysYunes Thanks! I suppose another way around it would be to convert the initial amount to thousands of dollars, so 100 in my case. This solves fine.

Yes, indeed. Sometimes if you scale the numbers yourself so that the difference between the smallest and the largest number in the data is reduced, this kind of bug goes away. Good thinking!

If by "two plants" you mean two different products whose inventories have to be tracked, you can simply duplicate the variables and repeat the same set of constraints for each product individually.

@@TallysYunes It's more transshipment in my case. Solver cannot find a solution.

Check out the transshipment example on my playlist (if you haven't yet) and double check that all your constraint formulas are correct. If it can't find a solution, there's at least one constraint that is being too strict.

This problem has alternative optimal solutions. As long as you still get 22.333 in cell H16 and all the constraints are satisfied, you're fine.

@@TallysYunes thank you!

This is caused by the problem being over constrained and the issue is with one of the (or a group of the) constraints. What I usually do is this: go to the grey area (i.e. the variables), start with it empty, and then assign some simple values to the grey cells (for example 1 or 2) and check that the resulting calculations that use those cells are returning the values you'd expect to see. Or try inputting a solution that you know should be feasible and then see if some calculated number looks weird. For instance, in this problem, type in the gray area a solution that only makes one type of gasoline. Try this with all gasolines (one at a time). You'll eventually find out where the issue is. In the worst case, go back to the beginning of the video and double check that all the formulas you are typing match mine exactly. Good luck!

What are the 3 parameters of this triangular distribution?

Essentially I’m trying to model future growth in an industrial company that has historically (15 years data) varied from -2% to +8% with median at 3%.

If the triangular function doesn't allow you to enter a negative for the low end, you can shift everything up 2% points and subtract afterward. For example: Cell A = randtriangular(0, 0.05, 0.1), and B = A - 0.02. This will make cell B behave as if it were a randtriangular(-0.02, 0.03, 0.08).

@@TallysYunes Thanks, Prof! Will try this.🙏

You're welcome!

I can't do homework for you, but it's likely that the one you need to tackle is similar to one of the examples in my videos. Look through my Excel Models playlist.

@@TallysYunes of course not! I'll be sure to check out the videos. I'm struggling with determining if it's blending or allocation, and determining the inequalities for blending. Especially when there's multiple rates and units of measurement. Do you offer tutoring?

At the moment I don't have time for one-on-one tutoring, but this is something your teacher would be able to clarify for you (it's their job). Have you tried reaching out to them? Do they offer office hours?

Thank you! I'm glad the videos are helping. Yes, you can add an "int" constraint on the gray cells. I don't do it in this video because I use this example to illustrate the ideas I go over at the end of the video to my students.

@@TallysYunes Can I ask what book you recommend? I see a few popular recommendations online. What would you choose?

Here's one that I like: www.amazon.com/Spreadsheet-Modeling-Decision-Analysis-Introduction/dp/130594741X

I don't have a detailed video on that, but at the beginning of this video I show you the mathematical formulation and the setup of the Solver window (you can pause the video at that moment and look at what I did). The formulas in column F and in cell B12 are all the same: a SUMPRODUCT. If you watch and understand the Farmer Problem example I have on this channel, you should be able to do this one.

In this case, you can deal with it as if it were two separate statements and it will result in two constraints: a) If we advertise on 3, we must also advertise on 9. b) if we advertise on 3, we must also advertise on 10. You can do each of the above with the "if this then that" formula that the video teaches.

You're welcome!

Thank you!

Thank you! There may be, but I'm not aware of any native Monte Carlo facilities for Excel other than the brute force way that can become very time consuming.

You're welcome!

Awesome! Thank you!

You're welcome.

Thank you! I'm happy to hear it helped!

I meant great playlist, not just this video. Doing a marathon of the playlist now :)