How good are you at calculating risk? - Gerd Gigerenzer

Prevodilac: Kristina Radosavljević Lektor: Ivana Krivokuća

A new drug reduces the risk of heart attacks by 40%.

Novi lek smanjuje rizik od srčanog napada za 40%.

Shark attacks are up by a factor of two.

Broj napada ajkula se dvostruko povećao.

Drinking a liter of soda per day doubles your chance of developing cancer.

Ispijanje litre gaziranih pića dnevno udvostručuje vaše šanse da dobijete rak.

These are all examples of relative risk,

Ovo su primeri relativnog rizika,

a common way risk is presented in news articles.

što je uobičajen način predstavljanja rizika po novinskim člancima.

Risk evaluation is a complicated tangle of statistical thinking

Procena rizika čini komplikovan splet statističkog razmišljanja

and personal preference.

i ličnih sklonosti.

One common stumbling block is the difference between

Jedan od uobičajenih kamena spoticanja

je razlika između relativnih rizika kao što su ovi

relative risks like these and what are called absolute risks.

i onoga što zovemo apsolutni rizici.

Risk is the likelihood that an event will occur.

Rizik predstavlja verovatnoću da će se neki događaj desiti.

It can be expressed as either a percentage—

Može biti izražen bilo u procentima -

for example, that heart attacks occur in 11% of men

na primer, da se srčani napad pojavljuje kod 11% muškaraca

between the ages of 60 and 79—

u dobi između 60 i 79 godina -

or as a rate— that one in two million divers along Australia’s western coast

ili kao stopa - da će, svake godine, jedan u dva miliona ronilaca

duž australijske zapadne obale pretrpeti smrtonosni napad ajkule.

will suffer a fatal shark bite each year.

These numbers express the absolute risk of heart attacks

Ove brojke izražavaju apsolutni rizik od srčanih napada

and shark attacks in these groups.

i napada ajkula u naznačenim grupama.

Changes in risk can be expressed in relative or absolute terms.

Promene u rizicima mogu se izraziti u relativnim ili apsolutnim oblicima.

For example, a review in 2009 found that mammography screenings

Na primer, pregled radova iz 2009. godine pokazao je da pregled mamogramom

reduced the number of breast cancer deaths from five women in one thousand to four.

smanjuje broj smrti od raka dojke sa pet žena od hiljade na četiri.

The absolute risk reduction was about .1%.

Smanjivanje apsolutnog rizika je iznosilo oko 0,1%.

But the relative risk reduction from 5 cases of cancer mortality to four

Ali smanjivanje relativnog rizika sa pet smrtnih slučajeva od raka na četiri

is 20%.

je 20%.

Based on reports of this higher number,

Na osnovu izveštaja koji sadrže veće brojke,

people overestimated the impact of screening.

ljudi potcenjuju uticaj preventivnog snimanja.

To see why the difference between the two ways of expressing risk matters,

Da bismo uvideli zašto je važna razlika između ova dva načina izražavanja rizika,

let’s consider the hypothetical example of a drug

uzmimo u obzir hipotetički primer leka

that reduces heart attack risk by 40%.

koji smanjuje rizik od srčanog udara za 40%.

Imagine that out of a group of 1,000 people

Zamislite da bi u grupi od 1 000 ljudi

who didn’t take the new drug, 10 would have heart attacks.

koji nisu uzeli novi lek njih 10 imalo srčani udar.

The absolute risk is 10 out of 1,000, or 1%.

Apsolutni rizik je 10 na 1 000, ili 1%.

If a similar group of 1,000 people did take the drug,

Kada bi slična grupa od 1 000 ljudi uzela taj lek,

the number of heart attacks would be six.

broj srčanih udara bi bio šest.

In other words, the drug could prevent four out of ten heart attacks—

Drugim rečima, taj lek bi sprečio četiri od deset srčanih udara -

a relative risk reduction of 40%.

umanjenje relativnog rizika je 40%.

Meanwhile, the absolute risk only dropped from 1% to 0.6%—

Istovremeno, apsolutni rizik se smanjio samo sa 1% na 0,6% -

but the 40% relative risk decrease sounds a lot more significant.

ali umanjenje od 40% relativnog rizika zvuči mnogo značajnije.

Surely preventing even a handful of heart attacks,

Svakako da je sprečavanje čak i nekolicine srčanih udara,

or any other negative outcome, is worthwhile— isn’t it?

ili bilo kog negativnog ishoda važno, zar ne?

Not necessarily.

Pa i ne baš.

The problem is that choices that reduce some risks

Problem je u tome što vas izbori koji smanjuju neke rizike

can put you in the path of others.

mogu izložiti drugim rizicima.

Suppose the heart-attack drug caused cancer in one half of 1% of patients.

Recimo da lek za sprečavanje srčanog udara

izaziva rak kod polovine od onih 1% pacijenata.

In our group of 1,000 people,

U našoj grupi od 1 000 ljudi,

four heart attacks would be prevented by taking the drug,

četiri srčana udara bi bila sprečena uzimanjem ovog leka,

but there would be five new cases of cancer.

ali bismo imali pet novih slučajeva raka.

The relative reduction in heart attack risk sounds substantial

Smanjenje relativnog rizika srčanog udara zvuči značajno,

and the absolute risk of cancer sounds small,

dok apsolutni rizik od raka zvuči minorno,

but they work out to about the same number of cases.

ali na kraju oni dovode do gotovo istog broja slučajeva.

In real life,

U stvarnom životu,

everyone’s individual evaluation of risk will vary

individualna procena rizika varira kod svakog,

depending on their personal circumstances.

zavisno od ličnih okolnosti osobe.

If you know you have a family history of heart disease

Ako znate da imate porodičnu istoriju srčanih oboljenja,

you might be more strongly motivated to take a medication

možda ćete imati malo jači motiv da uzmete lek

that would lower your heart-attack risk,

koji smanjuje vaš rizik od srčanog udara,

even knowing it provided only a small reduction in absolute risk.

iako znate da on obezbeđuje samo malo smanjenje apsolutnog rizika.

Sometimes, we have to decide between exposing ourselves to risks

Ponekad moramo da odlučimo između izlaganja sebe rizicima

that aren’t directly comparable.

koji nisu direktno uporedivi.

If, for example, the heart attack drug carried a higher risk

Ako, recimo, lek za srčani udar nosi visoki rizik

of a debilitating, but not life-threatening,

nanošenja štete zdravlju koja nije opasna po život,

side effect like migraines rather than cancer,

nuspojava poput migrene, umesto raka,

our evaluation of whether that risk is worth taking might change.

naša procena o tome da li vredi preuzeti taj rizik mogla bi da se promeni.

And sometimes there isn’t necessarily a correct choice:

Ponekad ne postoji nužno ispravan izbor:

some might say even a minuscule risk of shark attack is worth avoiding,

neki će reći da je čak i minimalan rizik od napada ajkule vredan izbegavanja,

because all you’d miss out on is an ocean swim,

jer jedino što ćete propustiti je plivanje u okeanu,

while others wouldn’t even consider skipping a swim

dok drugima neće padati na pamet da propuste to plivanje

to avoid an objectively tiny risk of shark attack.

da bi izbegli objektivno mali rizik od napada ajkule.

For all these reasons, risk evaluation is tricky at baseline,

Zbog svega ovoga, procena rizika je u suštini teška,

and reporting on risk can be misleading,

a izveštavanje o riziku može biti pogrešno protumačeno,

especially when it shares some numbers in absolute terms

pogotovo ukoliko se dele neke brojke koje se odnose na apsolutne oblike,

and others in relative terms.

a druge na relativne oblike rizika.

Understanding how these measures work

Razumevanje kako ove mere funkcionišu

will help you cut through some of the confusion

pomoći će vam da razjasnite neke nedoumice

and better evaluate risk.

i da bolje procenite rizik.