# Statistical Correlation between ordered SKUs

A

Hi All,
i have 320 SKUs in my warehouse. Customers place orders for about ~10 SKU on each and there is round 50 orders/day.
I'd like to check if there is say...90% probability when Customer orders SKU 100097 he will also order 100087 (for example) on the same order.

I plan to reorganize my WHS and having rotation ABC done, i'd like to know which SKUs i should place near to each other as they go together often.

How to do that?

#### Ninja

##### Looking for Reality
Staff member
Super Moderator
Re: Statistical Correlation between orderded SKUs

Great approach!

What you are trying to do is one of the main reasons databases were created...to mine the data looking for relationships and conflicts.

Short of that, poll your order pickers. They probably recognize some of these relationships and you may get a free head start for what you're after. People who do repetitive tasks like order picking tend to "get in a rut"...ask the pickers about the ruts they have noticed.

#### Steve Prevette

##### Deming Disciple
Staff member
Super Moderator
Re: Statistical Correlation between orderded SKUs

I suspect the best way to do this may be by pair-wise data. If a customer orders A, D, and G in one order, that is an A-D pair, a D-G pair, and a A-G pair. Once you have converted the orders to pairs (this should be accomplishable with an excel macro) then count up the most common pairs.

I don't know if you may also need to look at triples, quadruples, etc. For example, if one customer orders A and D, and a second D and G, and a third A and G, that would be treated the same was as if one customer ordered A, D, and G.

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
Steve has it exactly.

there may be an elegent program outthere or perhpas someone can write one for you but you can probably do this manually long befroe the elegant solution is available to you.

#### Steve Prevette

##### Deming Disciple
Staff member
Super Moderator
Interesting thing - just after answering this question I ended up with a similar question at work about how to group some like results in medical data. Didn't take too long to set up pairs for about 16 items (16 x 15 pairs) and use some array formulae count them up.

320 definitely would require resorting to a macro to identify the pairs, but is do-able in Excel.

#### Statistical Steven

##### Statistician
Staff member
Super Moderator
Hi All,
i have 320 SKUs in my warehouse. Customers place orders for about ~10 SKU on each and there is round 50 orders/day.
I'd like to check if there is say...90% probability when Customer orders SKU 100097 he will also order 100087 (for example) on the same order.

I plan to reorganize my WHS and having rotation ABC done, i'd like to know which SKUs i should place near to each other as they go together often.

How to do that?
Methods like logistic regression and some multivariate methods might assist in this process. You need to expand the analysis to more than just pairwise comparison and determine if there are any higher order relationships (3 SKUs, 4 SKUs, etc) which is abour ~430,000,000 comparisons (~51,000 just for pairwise comparisons). Supermarkets and Home Improvement stores have been doing this analysis for a long time and it usually requires a data warehouse to run this models. This is NOT a trival analysis. It took 5 full time SAS programmers 2 months to mine a 18 million record with 500 variable warehouse for this associations.

A

Thanks guys,
I was hoping i can pull the data, load to Minitab, run a fancy test and get it...fool me
Will go with some manual calculations i have selected ~60 A rotation SKU, will start with them and let you know results, if any

#### Miner

##### Forum Moderator
Staff member
You can reduce the effort by sorting based on volume. The old 80/20 rule still works (i.e., 20% of your SKUs will account for 80% of your volume).

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