Careful with Numbers
Their Meaning Is Not Always Clear!
science and math, data is often presented in the form of numbers, which
seem to be objective and precise. But is the true meaning of numbers always
clear? Can numerical data be open to different interpretations? Can numbers
even be misleading?
Counts--What Do The Numbers Really Mean?
graph to enlarge
example of numerical data to think about is the annual Synoptic Survey
of the Florida Manatee. This count has been conducted almost every year
since 1991 by the Florida Marine Research Institute (FMRI), whose scientists
(with help from numerous other cooperating agencies and scientists) make
a statewide count of manatees over a 1-2 day period (sometimes more than
one count is done in a single year.)
completing its survey, the FMRI announces the total number of manatees
counted. Although this information seems to be a straight-forward piece
of objective data--the total number of manatees counted in that specific
survey--the meaning of the count is often a topic of strong debate in
Florida. When the most recent count number is compared to earlier counts,
different people think the same numbers mean different things.
What do you think the survey count numbers really, truly mean for the
population of the Florida Manatee? Is the population decreasing? Is it
increasing? Look at the yearly count data from FMRI below. Also be sure
to read the summary of both sides' arguments below. Think about what the
scientists say the counts are really meant to measure,
and what the counts are not meant to measure. Then discuss:
the data really support either side's argument?
it fair to use the data for either side's argument?
there more data that needs to be looked at and considered?
Remember: Numbers seem to be very precise and objective, but
their true meaning is not always clear.
These groups are concerned that the manatees are endangered and they need
additional measures to protect them, such as speed zones, sactuaries,
and refuges, and added enforcement too.They generally say:
The annual counts only measure one thing--the number of manatees that
were visible on a specific day.
The number of manatees that are visible for a count can be significantly
influenced--upward or downward--by weather conditions, so the total
count of manatees may be the result of weather, and not a true count
of the whole manatee population. Therefore, higher counts do not necessarily
prove that there is a growing population of manatees.
The total population of manatees is only several thousand, which is
the entire population of the Florida manatee. With an endangered species,
having only a few thousand left on our entire planet is just too close
to extinction, and we should not take any chances by reducing protections.This
is especially important because sometimes nature itself has taken several
hundred manatees in one year due to such things as red tide.
Additional kinds of data should be considered when analyzing the size
and trend of manatee population, such as annual manatee mortality counts.
And we must remember the fact that manatees reproduce very slowly.
Marine Development, Angling and Recreation Groups:
These groups are concerned that measures to protect manatees
like speed zones, construction bans, sanctuaries, refuges, etc. interfere
too much with other activities like development, boating, fishing etc.
These groups look at the count data and focus on the numerical "fact"
that in the last several years there have been some of the highest counts
ever. They generally argue that this data means:
The population of manatees is growing because over the years the total
counts have generally increased;
Manatees are not endangered anymore, because these annual counts are
going up; and
Manatees therefore don't need as many protection measures.
to figure how someone would gather or compile the data they want you to
listen to, or in other words what "method" would be used. For
instance, one common advertisement said "four out of five dentists
surveyed would recommend sugarless gum for their patients who chew gum."
How do you think they gathered the data to make that statement? Would the
results have been any different if they had asked the Dentists about sugarless
mints instead of gum? Can you think of any other examples in the news on
data that you might want to question the method for?
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