Distributing Demand through the week

[Bushy]

Hi all,

If weekly demand for a product is over five work days and assuming a bank holiday on a Thursday does not affect the weekly demand of 370 how should the total be distributed through the week ignoring Thursday?

Example

A normal week

	Demand	Distribution factor
Mon	100​	1.351351​
Tue	80​	1.081081​
Wed	80​	1.081081​
Thu	60​	0.810811​
Fri	50​	0.675676​

With no Thursday demand should the new distribution factors (yet to be decided) add to 4 given we have removed a day or can it be kept at 5, either way will give the total demand required but which is mathematically correct?

 

[Klaas van Aarsen]

Hi all,

If weekly demand for a product is over five work days and assuming a bank holiday on a Thursday does not affect the weekly demand of 370 how should the total be distributed through the week ignoring Thursday?

Example

A normal week

	Demand	Distribution factor
Mon	100​	1.351351​
Tue	80​	1.081081​
Wed	80​	1.081081​
Thu	60​	0.810811​
Fri	50​	0.675676​

With no Thursday demand should the new distribution factors (yet to be decided) add to 4 given we have removed a day or can it be kept at 5, either way will give the total demand required but which is mathematically correct?

Hi Bushy!

Both methods will give the same answer.
They are mathematically equivalent.
So both are mathematically correct.

 

[Bushy]

Would you favour a particular method?

 

[Klaas van Aarsen]

Would you favour a particular method?

For myself I would prefer a third method.

Leave the distribution factors as they are, except for Thursday for which the factor will become zero.
Then calculate the new demand for each day with:

$\text{Demand} = \dfrac{\text{Distribution factor}}{\text{Sum of all distribution factors}} \times 370$

As you can see, there is no 4 or 5 involved.

Originally, the distribution factors were calculated from the actual demand.
Now that you want to create a forecast for a week with a bank holiday, that forecast is based on the previously calculated distribution factors.
I feel that they should not be changed to find the new demand - they are your input.