Today’s headline is a true proposition. “Probably fine” isn’t a number, yet it is a perfectly reasonable way to communicate risk. Indeed most risk is, and should be, given in the form of words, or even vague thoughts.
What is to be discouraged is the relentless, brutal search for scientific-sounding precision which, unless the situation is rigorously defined, is absurd and leads to bad decisions.
The proof of this is easy. Take the context from where the quote originated, a Wall Street Journal article by a once-pregnant lady (Emily Oster) who was investigating the myriad restrictions and cautions issued to women who wish to take care of the lives growing inside them. Oster asked her doctor whether she could have “one or two glasses” a wine a week, to which the doctor replied that it was “probably fine.”
This led Oster to observe that “probably fine” was not a number, which was less than satisfying. She desired “real answers.”
In her pursuit of real answers, Oster discovered in medical journals that some deli meats had the risk of carrying listeria bacteria, which is bad.
I concluded that avoiding queso fresco and deli turkey was a good idea, but in the end I didn’t feel that it made sense even to exclude other deli meats. My best guess was that avoiding sliced ham would lower my risk of listeria from 1 in 8,333 to 1 in 8,255. I just didn’t think it was worth it. It would have made more sense to avoid cantaloupe.
Here are two “real” answers: 1 in 8,333 and 1 in 8,255. Each a nice quantification and, as promised, both give the feeling that science is happening. Both are also absurdly, unjustifiably precise.
These numbers were culled from various medical studies. Now any study is conditional (as all probability is conditional) on the kind and type of observations that were taken. For instance, in studies of deli meats containing listeria, there are the kinds of meats—all the different kind of hams, bologna, including that with and without olives or other stuffings, various types of turkey, salted beef, hard salamis, soft ones. There are different manufacturers—domestic, international, the actual plants, the carriers and methods of transport to the delis.
There are the animals used in the meats—pigs, cows, mystery meats, each of these grown on farms God knows where, each fed different foods, some genetically this way, others genetically that, some fed with antibiotics in various doses, some given hormones.
Then there are the delis—located in this and that neighborhood, kept under who knows what temperature control, selling meats fresh and past its sell-by dates, owned by fastidious shopkeepers or by corporations, managed by new hires and old. There are many more items easily added to the list which are is possible to imagine influence the chance a given piece of meat contains listeria.
In the end we have a piece of meat from a deli. Either it will have listeria or it will not (a tautology, therefore always true of any piece of meat). If it does, we look at all the characteristics listed above and put a check mark next to the ones which are true of this slice (from a pig, sold on a weekend, etc.). One of these characteristics might have been the cause of the meat having listeria, or maybe we missed measuring the cause, and that the characteristics we measured are only associated with the cause.
A second piece of meat won’t have listeria. Again we check off all the boxes, some of which will be also checked in the meat with listeria, some won’t. If boxes are checked for both pieces, it seems likely that those characteristics aren’t the one that caused or didn’t cause the bacteria to grow. But some characteristics will be checked on the bacteria-laden meat which won’t be checked on the clean meat, and vice versa. Perhaps one of these, or lack of one of these, is why the meat got infected. It is only “seems likely” and “perhaps” because we have to recall that we might not have measured all the right things.
In the end, we have to pick some characteristics and eschew others; we have to settle for summaries. For example, in one experiment we might find a greater frequency of turkey slices than ham slices contained listeria. The risk of eating turkey or ham can thus be given a precise number. But because this summary necessarily ignores many characteristics, and we are never sure we have thought of every relevant one, the quantification is only meaningful if it is certain that characteristics we ignored or didn’t measure where not involved in listeria production.
Since we are not certain, the quantification is the wrong number: it is not the real answer. It is misleading, it is too sure. Better to round to the nearest order of magnitude. Or say something like “Eating a slice of deli ham is probably fine.”
And we haven’t even added the layers of complexity which comes from eating the meats! Some people can eat the bacteria-laden meat and never develop symptoms, others need only a fragment to become ill. Oh my! It goes on and on.
And so have I. So I’ll stop.
Thanks to reader Jim Fedako for suggesting this topic.