We've just heard from a friend of ours that her husband has a ninety per cent chance of being cancer-free after a course of radio- and chemotherapy. He was recently diagnosed as suffering from prostate cancer. I wonder what it really means? - to have a ninety per cent chance? Ninety per cent of what? The only thing that's hundred per cent certain (apart from taxes) is death. Does that mean he's more likely to die than recover, or recover than die, or recover then die?
And does the ninety per cent take into account his life expectancy anyway? He's sixty-one. Is he more likely to die of old age or something else before he recovers from this particular illness?
Percentages cannot be applied comfortably, let alone accurately, to human life. We acknowledge this implicitly by omitting in a case like this any consideration of a wife's committment to her husband's survival. If asked, she might reply that it is one hundred and ten per cent! So much for mathematics.