48$z$ test statistic

$\displaystyle H_0\colon \mu = 50$. A sample of 64 has mean 52, and $\displaystyle \sigma = 8$. Find the $\displaystyle z$ test statistic.

The z statistic shows how many standard errors x̄ is from μ: z = (x̄ − μ)/(σ/√n). Here σ/√n = 8/8 = 1, so z = (52 − 50)/1 = 2.