The Z-Test Calculator determines whether there is a significant difference between a sample mean and the population mean when the population standard deviation is known. It calculates the Z-value using the standard formula Z=(xˉ−μ)σ/√nZ = \frac{(x̄ – μ)}{σ / √n}Z=σ/√n(xˉ−μ)​. This value can then be compared to a critical Z-value to evaluate whether the sample provides enough evidence to reject the null hypothesis. It’s useful in hypothesis testing for large samples or when population variance is known.