Uncertainty in Science

Another Kind of Shades of Gray: 

Uncertainty in Earth Science and how we teach it

You may remember the Italian geoscientists who were convicted of manslaughter in October of 2012 for failing to warn the public about an earthquake that struck L’Aquila, Italy in 2009.  I remember the dismay I felt, given the complexity of Earth’s systems, that people would expect such certainty from science.  I wondered if the human need for certainty is part of our nature, or if the way we teach science contributes to the public’s misperception that science is never ambiguous.

 This week, I read Naomi Lubick’s article “Be Prepared: Navigating the risks of hazards research” in the January 2014 edition of Earth (http://www.earthmagazine.org/article/be-prepared-navigating-risks-hazards-research).  She explores the thicket of misunderstanding that exists between scientists’ understanding of “uncertainty” and the public’s need to have answers in black and white.  The article reminded me of those questions and made me think about the difficulty my students have in understanding uncertainty.

Recently, I had students read eyewitness accounts of earthquake damage and estimate the intensity of shaking based on the qualitative Modified Mercalli scale.  To help them evaluate their judgments, we reviewed the “answer key”, but, because data from some locations was inadequate for determining the Mercalli ranking, a question mark replaced some answers.  A student told the class “I think I’m uncomfortable with the answer key having question marks.”  Students don’t expect uncertainty in science.  Students think that in science there is right, and there is wrong.  There are no question marks.

Some things we don’t know about earthquakes.  Other things we do know, and with a high degree of certainty.  But some things, we know only with a significant measure of uncertainty.  It is the last of these that are hardest to teach or to convey to the public.  Perhaps one approach is to point out that scientists don’t claim to be able to predict earthquakes exactly, but they do have some ability to predict earthquakes within uncertainty limits.  For example, the legend to the 2008 United States National Seismic Hazard Maps ( USGS) states “Colors on this map show the levels of horizontal shaking that have a 2-in-100 chance of being exceeded in a 50-year period.” However, just stating probabilities doesn’t necessarily convey meaning, especially for middle and high school students.  How exactly can teachers help students understand what this statement means?

Maybe one way to help students understand uncertainty is through a variation of the common math exercise of flipping coins.  Instead of flipping one penny 10 times, consider flipping 10 pennies at the same time.  How many of them will come down heads?  Well, on average, 5.  But in practice, it will only be 5 about a quarter of the time.  It will be either 4 or 6 about 41% of the time (66% chance of being within “1” of 5).  And it will be 3 or 7 about 23% of the time (an 89% chance of being within “2” of 5).  Even though our answer of “five on average” is quite true, there is an uncertainty in our prediction.  Likewise with earthquakes, we may know what’s going to happen on average, but predicting exactly what will happen and when is uncertain.

What have you tried that helps students understand uncertainty?  How did it work?  Does our responsibility to teach “correct information” get in the way of exploring how science works? Please share!



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One thought on “Uncertainty in Science

  1. I am not a teacher, but I will play around with the topic Mary brings up. Emphasis on the ‘play’ here (you have been warned).
    It is interesting that science and scientists can not just admit to uncertainty, but
    in some cases, uncertainty has been enshrined in a given field of study. The
    “Uncertainty Principle” in quantum mechanics, as first espoused by a German
    scientist in 1927, asserted that just via the act of observation it could be difficult
    if not impossible to ‘know’ something for a certainty when the observation is causing it’s own disruption to the system you are trying to observe. One can get
    a sense of the truth of that when us ‘macro’ people are dealing with micro-particles on such a small scale as quantum mechanics is concerned with.
    And while it is a stretch, it is also the case with human psychological studies
    that another kind of ‘observer effect’ kicks in, where people will respond differently to a given situation or series of questions based on whether they think
    they are being observed or monitored by others, or feel they need to respond in
    the manner the questioner expects them to. Often a study will be conducted, not
    to answer the questions asked of the participants, but to let the questions asked
    mislead the participants into thinking they know what is going on, simply to get
    at an impartial and unbiased answer to what the study is really about. This is a
    method of taking the observer effect (one hopes) out of the equation.
    Neither instance here, on either the micro-physical or macro-psychological
    scale, pertains directly to the Italian case of geoscientists being convicted for
    not warning the public of an earthquake beforehand, but it does go to the idea
    that not only do scientists in general have to grapple with uncertainty to an extent
    that the general public either isn’t aware of or doesn’t want to acknowledge, but
    that ‘uncertainty’ can almost act as its own entity, a direct obstacle and tangible
    presence to be dealt with, if possible, by scientists the world over in more fields
    of study than I have mentioned here.
    In the ‘field’ of pop culture, the perceived notion of uncertainty and scientists
    can turn even more dire. The 1982 pop hit song “She Blinded Me With Science”
    construes scientists (or maybe it is just women scientists!) as persons bent on
    malevolence, or at least the continued ignorance of the general masses, which
    is apparently the verdict reached in the Italian case of the ‘failed’ earthquake
    warning. Half of Hollywood would be out of business if not for the dependable
    malevolence of deranged scientists towards their fellow man, and usually ALL
    7 billion of us (the go big or go home theorem). While it could be silly to bring
    up pop culture references here, don’t underestimate the general low esteem
    they can cause science and scientists to be held in, and how this will seep in
    to any intersection between non-scientists and, literally here, a judgment made
    by same on scientists.
    To conclude my words here, and again at the risk of flying about on the topic,
    it simply isn’t possible for me to contribute on the subject of ‘uncertainty’ that Mary has brought up without quoting the words of former Secretary of Defense Donald Rumsfeld in 2002, on the 75th anniversary of the “Uncertainty Principle” (see how I cleverly tied that together?). In regards to a question on the ‘War On Terror’ and intelligence reports, Rumsfeld responded in part “….as we know, there are known knowns, there are things that we know that we know. We also
    know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don’t know we don’t know.”
    For the purposes of our discussion, the ‘known known’ would be the eerie
    parallels between ‘The War On Terror’ and teaching Earth Science to middle-
    schoolers. (I had to throw you teachers a bone) The ‘known unknown’ is
    whether Donald Rumsfeld would have made a better expert for the defense or
    prosecution in the Italian geoscientist case. The ‘unknown unknown’ here by
    definition escapes me.

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