Thank you for the lecture , it was so helpful especially during these tough times. However I do have a question . In the example you did you had 69.20 as the time for the 30th batch however when I used my own calculator I got 68.91 , a difference of .29 . Is there an allowance for answers as such during the marking of exams?

Thank you John for this lecture, i have a question with regards to finding log in exams for CBE format exam. Is there a way how can we find log on excel (i believe they have limited excel formulas to an extent)
Are we also allowed scientific calculators in CBE exam? Please guide

The spreadsheet in the exam is not Excel. It is similar but does not have built in formulae. You are allowed to have a scientific calculator in the exam (and you need one).

Another question,
What is the difference between cumulative average hours per unit which equal to 90.08 hrs and average time for 30th 69.20 hrs.
Could you make it clear plz.

My question regarding budgeting of time for a new product (Ex2 in this lecture).

We know about canceled of learning factor from 30th unit and calculated the number of hours which should be appear in the production plan for total number of unit.
However, we know that first 29th of unit will take more time.
Should I present it in my budget?
For example, I asked calculated the total production time for 1000 of unit in this example.
My calculation would be 1000*69.20 or (1000-29)*69.2+29*90.8?

Hello John sir,
How are you?
I hope you are doing well,
For the example 3 part (b) you got the average time per unit number 30 by getting the cumulative average total time for 30 units and subtract the cumulative average total time for 29 unit which equal to 69.20 hrs.
My question is I used the doubling method, I calculated the cumulative average total hours for 32 units and also I calculated the time spent for the most recent units I mean for the most recent 16 units (from 17 to 32) which equal 1169.294 and I divided on 16 unit to get the average time spent on unit number 30 but the result comes different I got 73.1 hrs.
So what is the mistake that I have already done?

Hi John,
As we’d be doing most of the workings on the spreadsheet provided, wouldn’t it be easier to calculate x to the power y on the spreadsheet instead of using a calculator?
In this example, we’d simply type out “=30^-0.2345” on the spreadsheet and hit enter.
Thanks.

I just thought it would be useful to point out that when we use the doubling method we can multiply a by our rate to the power required. Using the example given we would get 200×0.85^4 = 104.40.

You can always use the formula, but if it does involve doubling then it is easier to use the doubling rule. The question will not tell you which approach to use – that is up to you to check (and it should be obvious always if it involved doubling).

The exception is when the question asks you to calculate the learning rate. That will always be using the doubling rule – you cannot be asked to use the formula ‘backwards’ 🙂

Dear John!
Part A, example 3. Doubling Rule gives 1470.42 as the time for the next 15 batches. However, if i use the formula I get 15 X 105.99 = 1589.89. What am I missing / doing wrong here?

The formula just gives you the average time per batch. So you still have to calculate the average time per batch for 16 batches, then multiply by 16 to get the total time for 16 batches, and then subtract the time for the first batch (so as to end up with the time for 15 batches).

(The answer might still end up being slightly different, but that will then be simply due to rounding.)

Thank you, I got confused with part B of the example 3 where we use the formula for 30 and 29 batches and the subtract one result to the other. But I guess it has to do with the fact that the learning curve cease at the 30th. Am I right?

Yes (although only because we need the time for the 30th batch, because that is the time for all future batches).

Whether using the doubling rule or using the formula, that only gives us the total time for the total number of batches. For any others (whether it be like part (a) or like part (b)) we need the difference between the two total times.

Hello! I wasn’t 100% sure if I should ask this in the forum or on the lecture notes so I apologise in advance!

In regards to the learning rate, can we just learn the doubling rule or would we be expected to learn the learning rate formula to calculate additional time for nth unit, which in the BPP text is shown as;

=(n x t2) – [n-1) x t1]

cumulative average time for first (n-1) units = t1
total time for first (n-1) units = (n-1) x t1
cumulative average time for first n units = t2
total time for first n units = n x t2

If you have watched all my lectures on this, then you will know that you need to know how to use both the doubling rule and the formula given on the formula sheet.

The formula you quote from BPP is not something to learn because if you understand what I explain in the lectures, then it is obvious – it is silly to learn formula for the sake of learning. Most of the exam is testing that you understand what is happening – not that you have learned formulae – which is why only 50% of the exam involves calculations.

Very nice lecture and very helpful.
As time total per unit, we can rearrange formula y=ax^(b+1). When “y” is total time hours not average time per unit!

agboolakenny84 says

Good day Mr John

This may seem like a silly question but I don’t know how you got 150 hours for 2 units and 225 for 4 units.

agboolakenny84 says

Ooh, you multiplied it.

John Moffat says

Yes 🙂

faithnderitu says

Thank you for the lecture , it was so helpful especially during these tough times. However I do have a question . In the example you did you had 69.20 as the time for the 30th batch however when I used my own calculator I got 68.91 , a difference of .29 . Is there an allowance for answers as such during the marking of exams?

John Moffat says

Yes – small rounding differences are not relevant 🙂

vidhi05255 says

Thnakyou for quick response

John Moffat says

You are welcome 🙂

vidhi05255 says

Thank you John for this lecture, i have a question with regards to finding log in exams for CBE format exam. Is there a way how can we find log on excel (i believe they have limited excel formulas to an extent)

Are we also allowed scientific calculators in CBE exam? Please guide

John Moffat says

The spreadsheet in the exam is not Excel. It is similar but does not have built in formulae. You are allowed to have a scientific calculator in the exam (and you need one).

7fsa says

Another question,

What is the difference between cumulative average hours per unit which equal to 90.08 hrs and average time for 30th 69.20 hrs.

Could you make it clear plz.

John Moffat says

The first batch takes 200 hours. Each extra batch takes less and less time and the 30th batch only takes 69.20 hours.

90.08 hours is the average time per batch for all the batches made, which will therefore be somewhere between 200 and 69.20.

7fsa says

Thank you sir, thank you so much.

vikulchik07 says

Hello!

My question regarding budgeting of time for a new product (Ex2 in this lecture).

We know about canceled of learning factor from 30th unit and calculated the number of hours which should be appear in the production plan for total number of unit.

However, we know that first 29th of unit will take more time.

Should I present it in my budget?

For example, I asked calculated the total production time for 1000 of unit in this example.

My calculation would be 1000*69.20 or (1000-29)*69.2+29*90.8?

Thanks in advance!

Best regards,

Victoria

7fsa says

Hello John sir,

How are you?

I hope you are doing well,

For the example 3 part (b) you got the average time per unit number 30 by getting the cumulative average total time for 30 units and subtract the cumulative average total time for 29 unit which equal to 69.20 hrs.

My question is I used the doubling method, I calculated the cumulative average total hours for 32 units and also I calculated the time spent for the most recent units I mean for the most recent 16 units (from 17 to 32) which equal 1169.294 and I divided on 16 unit to get the average time spent on unit number 30 but the result comes different I got 73.1 hrs.

So what is the mistake that I have already done?

John Moffat says

Each batch they make takes less time. So the 17th will be faster than the 16th, the 18th will be faster than the 17th, and so on.

We need to know how long the 30th batch will take, which is bound to be less time than the average of the 16th to 30th times.

7fsa says

I got you,Thank you sir, thank you so much.

7fsa says

Hello John sir,

Thank you so much for your informative lecture.

John Moffat says

Thank you for your comment 🙂

espie says

Hi John,

As we’d be doing most of the workings on the spreadsheet provided, wouldn’t it be easier to calculate x to the power y on the spreadsheet instead of using a calculator?

In this example, we’d simply type out “=30^-0.2345” on the spreadsheet and hit enter.

Thanks.

vidhi05255 says

But how do we find log on spreadsheet??

John Moffat says

You don’t with the spreadsheet in the exam. You need a scientific calculator.

adch111 says

I just thought it would be useful to point out that when we use the doubling method we can multiply a by our rate to the power required. Using the example given we would get 200×0.85^4 = 104.40.

Felistus says

hi John

How do i know when i should apply the y=axb formula or the doubling formula

John Moffat says

You can always use the formula, but if it does involve doubling then it is easier to use the doubling rule. The question will not tell you which approach to use – that is up to you to check (and it should be obvious always if it involved doubling).

The exception is when the question asks you to calculate the learning rate. That will always be using the doubling rule – you cannot be asked to use the formula ‘backwards’ 🙂

francihco says

Dear John!

Part A, example 3. Doubling Rule gives 1470.42 as the time for the next 15 batches. However, if i use the formula I get 15 X 105.99 = 1589.89. What am I missing / doing wrong here?

John Moffat says

The formula just gives you the average time per batch. So you still have to calculate the average time per batch for 16 batches, then multiply by 16 to get the total time for 16 batches, and then subtract the time for the first batch (so as to end up with the time for 15 batches).

(The answer might still end up being slightly different, but that will then be simply due to rounding.)

francihco says

Thank you, I got confused with part B of the example 3 where we use the formula for 30 and 29 batches and the subtract one result to the other. But I guess it has to do with the fact that the learning curve cease at the 30th. Am I right?

John Moffat says

Yes (although only because we need the time for the 30th batch, because that is the time for all future batches).

Whether using the doubling rule or using the formula, that only gives us the total time for the total number of batches. For any others (whether it be like part (a) or like part (b)) we need the difference between the two total times.

darciecoco says

Hello! I wasn’t 100% sure if I should ask this in the forum or on the lecture notes so I apologise in advance!

In regards to the learning rate, can we just learn the doubling rule or would we be expected to learn the learning rate formula to calculate additional time for nth unit, which in the BPP text is shown as;

=(n x t2) – [n-1) x t1]

cumulative average time for first (n-1) units = t1

total time for first (n-1) units = (n-1) x t1

cumulative average time for first n units = t2

total time for first n units = n x t2

Hopefully this makes sense!

Thank you.

John Moffat says

If you have watched all my lectures on this, then you will know that you need to know how to use both the doubling rule and the formula given on the formula sheet.

The formula you quote from BPP is not something to learn because if you understand what I explain in the lectures, then it is obvious – it is silly to learn formula for the sake of learning. Most of the exam is testing that you understand what is happening – not that you have learned formulae – which is why only 50% of the exam involves calculations.

alie2018 says

Thanks John.

alie2018 says

The most important thing to know is when to apply the formula and when not to, depending on the prevailing circumstances.

dleka says

Very nice lecture and very helpful.

As time total per unit, we can rearrange formula y=ax^(b+1). When “y” is total time hours not average time per unit!

John Moffat says

You can, but do not simply learn formula – the examiner is clever at testing your understanding 🙂