Inventory Sample Size Calculator

Formula

The formula to calculate the inventory sample size is:

\[ n = \frac{{Z^2 \cdot p \cdot (1-p)}}{{e^2}} \cdot \frac{{1}}{{1 + \left(\frac{{n - 1}}{{N}}\right)}} \]

Where:

\(N\) is the population size
\(Z\) is the Z-score associated with the desired confidence level
\(p\) is the estimated proportion of the attribute present in the population (typically 0.5 for maximum variability)
\(e\) is the margin of error

What is the Inventory Sample Size?

Inventory sample size is the number of items from a larger population of inventory that should be audited to estimate the characteristics of the whole inventory with a certain level of confidence. It is a crucial concept in inventory management, quality control, and statistical sampling.

Example Calculation

Let's assume the following values:

Population Size (N) = 1000
Z-score (Z) = 1.96 (for a 95% confidence level)
Estimated Proportion (p) = 0.5
Margin of Error (e) = 0.05

Using the formula:

\[ n = \frac{{1.96^2 \cdot 0.5 \cdot (1-0.5)}}{{0.05^2}} \cdot \frac{{1}}{{1 + \left(\frac{{n - 1}}{{1000}}\right)}} = \frac{{3.8416 \cdot 0.25}}{{0.0025}} \cdot \frac{{1}}{{1 + \left(\frac{{n - 1}}{{1000}}\right)}} = 384.16 \cdot \frac{{1}}{{1 + \left(\frac{{384.16 - 1}}{{1000}}\right)}} = 278 \]

The Sample Size (n) is 278.