Be Careful with Numbers
Their Meaning Is Not Always Clear!

In 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?

Manatee Counts--What Do The Numbers Really Mean?

 Click graph to enlarge

One 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.)

After 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.

Try This! Journaling Questions
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:

Does the data really support either side's argument?

Is it fair to use the data for either side's argument?

Is there more data that needs to be looked at and considered?

Always Remember: Numbers seem to be very precise and objective, but their true meaning is not always clear.

 Manatee High Counts 1991-2004
 1991 1,465 1992 1,856 1993 * 1994 * 1995 1,822 1996 2,639 1997 2,229 1998 2,022 1999 2,353 2000 2,223 2001 3,276 2002 1,796 2003 3,113 2004 2,568

Manatee Conservation Groups:
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:

1. The annual counts only measure one thing--the number of manatees that were visible on a specific day.

2. 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.

3. 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.

4. 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.

Some 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:

1. The population of manatees is growing because over the years the total counts have generally increased;

2. Manatees are not endangered anymore, because these annual counts are going up; and

3. Manatees therefore don't need as many protection measures.

More Journaling Questions
Try 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?