Can I get some statistics help

[AlKemp70]

Can I get some maths or statistics help here?

I have got A-level maths but only from back in 1989, so I am a bit rusty here. Although this means I can understand somewhat if the maths is worked through and explained.

I have a sideline in my business, selling vinyl and CDs on Discogs.

I only have slightly over 500 items on there.

I haven't had negative feedback since 2017. And even then I would only get this once a year or so.

I've sorted my stock-taking since then. But recently I got myself overworked and slipped up. I spread myself thin in other areas of the business.

And in the last 7 orders I have had had 6 out of stock in a row, with only one in stock.

I often buy 3 or 4 copies of each album, so relist them until they are gone. [Hence more than 500 items in my stockroom]


I am going to look at this as an anomaly for the moment before I get paranoid.

But I need to get my head around this, I can at the end of the day get past this issue so need to panic but...

What is the actual statistical significance of this occurring in this small a side-operation? There are 500 or so other items that have also sold in the past, and those orders that were out of stock aren't those products more commercial than any of the others.

So the maths would be with average sales over a period of 3 months when quiet (it's a sideline hence not a major problem getting past this issue) of only 2 1/2 sales a week. But I can have 1 or 2 sales a day during good periods.

When sales pick up they are all for items that are out of stock (which is rare for me - the last time this happened was after my father-in-law died)...

With 7 sales in the last 3 weeks, so business picking up

6 items are then out of stock

Of 500 items at least listed on a well-known platform [with multiple copies in the stockroom of those in stock in the stockroom]

I was just wondering if anyone enjoyed this type of 'cluedo' and enjoyed maths, what the statistic likelihood is.

Just to get a reality check, please! This is weird at least.

[I have over 11 years experience in this area of the business btw, I just ventured into other areas as well]



(given I haven't had any complaints for 7 years).

 

[DontAsk]

I think you are overthinking

Did the out of stock cause the customers to leave negative feedback?

Use your time to sort out your stock control.

 

[MikeJ]

Were they all for one or two items? Wondered if something had happened to cause a rush on a certain artist.

 

[AlKemp70]

Were they all for one or two items? Wondered if something had happened to cause a rush on a certain artist.

All were for just one, except one which was for two.

With the order where there were two items only one was out of stock, in that case, the cheaper item, but that was the one the customer was after, the other he bought to justify his purchase but was less bothered by, so I had to cancel.

All the orders were for different artists, and all were 'new' products (as in straight from the distributor rather than second-hand) but were released more than a couple of years ago.

So no sense on any rush on any particular artist

 

[BusterBloodvessel]

Firstly, I'm not sure why you want to find this % out, but anyway..... I don't actually know WHAT % you're trying to find out?

Do you want to know what the chances are of 6 out of 7 orders being out of stock? That's impossible to know without knowing how many of your 500 listings are out of stock.

 

[JEREMY HAWKE]

Have you considered some Warehouse software
Microsoft do some sort of bolt on to your existing system but my knowledge of stock control software is very limited but it does boarder onto transport management systems

 

[AlKemp70]

Firstly, I'm not sure why you want to find this % out, but anyway..... I don't actually know WHAT % you're trying to find out?

Do you want to know what the chances are of 6 out of 7 orders being out of stock? That's impossible to know without knowing how many of your 500 listings are out of stock.

in my stockroom, there are 5 crates of records (it's a sideline), in each crate there are approx 120 records.

all have been listed and will be in stock.

I am asking for an approximation.

The reason, I am asking is that it seems an anomaly.

I am technically not asking for a % though. I am asking for the statistical significance, I have also studied research methods.

I don't know you, so if you know this already apologies,

but from Investopedia this is why I am asking:

KEY TAKEAWAYS​

• Statistical significance refers to the claim that a result from data generated by testing or experimentation is likely to be attributable to a specific cause.
• A high degree of statistical significance indicates that an observed relationship is unlikely to be due to chance.

 

[cjd]

Assuming random buying and no re-stocking, the probability of an item being out of stock is n/500 where n=the number of items currently out of stock. The probability of the next item ordered being out of stock is (n/500) x (n/500). For 6 items ordered out of stock in a row the probability is as above done six times.

Unless you have a large number of items out of stock, that's going to be a highly improbable number. So it would suggest something is not random in the buying pattern.

 

[AlKemp70]

If that's the case then yes it IS a highly improbable number.

My calculator couldn't cope with the number of noughts after the first few 0.00000 etc.

Thanks for confirming how unlikely it is.

I will now have to think about how to proceed.

Much appreciated. I thought I was going mad!

 

[UKSBD]

Is it not as simple as;
An artist dies - sales of records increases - you run out of stock - next 6 orders are people ordering something out of stock

 

[cjd]

Ie it's a non-random buying pattern. Something's afoot.

 

[japancool]

in my stockroom, there are 5 crates of records (it's a sideline), in each crate there are approx 120 records.

I don't understand. Are you *only* listing the items you have in stock? Is your stock system linked to your sales system?

If it is, and every thing is working properly, you should never have anything out of stock. Have you done a stock take and reconciled against your stock system?

 

[WaveJumper]

I don't understand. Are you *only* listing the items you have in stock? Is your stock system linked to your sales system?

If it is, and every thing is working properly, you should never have anything out of stock. Have you done a stock take and reconciled against your stock system?

Yes surely it all about keeping good records ?