Suppose the background extinction rate of amphibians is 8 per 1,000 years and that during the twentieth century, 20 amphibians went extinct. The extinction rate of amphibians is now about how many times the background rate?

Question

Quizplus · Accepted Answer

The background extinction rate is 8 per 1,000 years, so the expected number of extinctions in the twentieth century is 8 * 100 = 800. The actual number of extinctions was 20, so the extinction rate is now about 20 / 800 = 1 / 40 = 0.025 times the background rate.

Suppose the Background Extinction Rate of Amphibians Is 8 Per