Say we calculated the incidence of orchitis in the whole population of the UK and got 12 cases per year per ten thousand people.

假设我们计算了英国总人口中睾丸炎的发病率，每万人中每年有 12 例。

Considering everyone in the UK might give us a misleading impression because we know about half of that group have no risk of developing orchitis.

但把全英国的人都算上其实是误导性的，因为我们知道大约一半的人没有患睾丸炎的风险。