existing statistics or on common sense are often very good predictors of
significant outcomes. In a memorable example, Dawes showed that
marital stability is well predicted by a formula:
frequency of lovemaking minus frequency of quarrelsYou don’t want your result to be a negative number.
The important conclusion from this research is that an algorithm that is
constructed on the back of an envelope is often good enough to compete
with an optimally weighted formula, and certainly good enough to outdo
expert judgment. This logic can be applied in many domains, ranging from
the selection of stocks by portfolio managers to the choices of medical
treatments by doctors or patients.
A classic application of this approach is a simple algorithm that has
saved the lives of hundreds of thousands of infants. Obstetricians had
always known that an infant who is not breathing normally within a few
minutes of birth is at high risk of brain damage or death. Until the
anesthesiologist Virginia Apgar intervened in 1953, physicians and
midwives used their clinical judgment to determine whether a baby was in
distress. Different practitioners focused on different cues. Some watched
for breathing problems while others monitored how soon the baby cried.
Without a standardized procedure, danger signs were often missed, and
many newborn infants died.
One day over breakfast, a medical resident asked how Dr. Apgar would
make a systematic assessment of a newborn. “That’s easy,” she replied.
“You would do it like this.” Apgar jotted down five variables (heart rate,
respiration, reflex, muscle tone, and color) and three scores (0, 1, or 2,
depending on the robustness of each sign). Realizing that she might have
made a breakequthrough that any delivery room could implement, Apgar
began rating infants by this rule one minute after they were born. A baby
with a total score of 8 or above was likely to be pink, squirming, crying,
grimacing, with a pulse of 100 or more—in good shape. A baby with a
score of 4 or below was probably bluish, flaccid, passive, with a slow or
weak pulse—in need of immediate intervention. Applying Apgar’s score,
the staff in delivery rooms finally had consistent standards for determining
which babies were in trouble, and the formula is credited for an important
contribution to reducing infant mortality. The Apgar test is still used every
day in every delivery room. Atul Gawande’s recent A Checklist Manifesto
provides many other examples of the virtues of checklists and simple rules.