An IRS auditor randomly selects 3 tax returns from 61 tax returns of which 9 contain errors. What is the probability that she selects all those containing errors? This is unusual probability?

\(p = \dfrac{\dbinom{9}{3}\dbinom{52}{0}}{\dbinom{61}{3}} = \dfrac{42}{17995} \approx 0.002334 = 0.2334\%\\ \text{So yeah, pretty small probability}\)