My company is trying to implement sample size counting to determine our inventory accuracy.

95% confidence level

2.5% confidence interval

I am struggling with how to determine the appropriate sample size for each of our warehouses. If I have four storage locations with inventories of:

- 248
- 734
- 3,911
- 9,756

and I want to be able to confidently say what our accuracies are for each of those locations, how can I calculate that? (bonus if you can help me with an Excel formula).

NOTE: Accuracy in this case means, when we go to the shelf and count an item, we either have the quantity we think we have in that location (accurate) or we don't (inaccurate).