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Understanding the Data

The LMVP data are typically graphed in 3 different ways. The most common graph shows seasonal variations (See 1 below). The parameter represented is named on the vertical axis, which is usually on the left. These graphs will show all of the data collected last year, with the date of collection shown at the bottom of the graph.

Some data are shown as trend graphs. Depending upon the amount of information we need to show we either use a stick plot (2) or a box plot (3).

The stick plot features a “stick” that reaches from the high value to the low value and a dot that shows the geometric mean for that year. Box plots convey a bit more information than stick plots. The “caps” at the top and bottom show the maximum and minimum values for the year. The “box” surrounds the middle half of the data. Finally, the line within the box shows the median, or middle, value.
For more information on box plots, visit: http://www.lmvp.org/boxplots.htm.

Each stick or box plot represents data from a single season. These plots will always be shown with other stick or box plots for comparison among years. When stick plots or box plots are shown, only the “summer” data are used. For our purposes, we define summer as the period between May 15 and September 15. This period is shown in section 1 of the figure below with the dotted lines, so in this case the samples from early May and early October would not be used. Trimming the data like this lets us compare data from different years, regardless of whether the volunteer began (or finished) sampling early (or late).

In the stick and box plots below, the take home point is that the data range from a low of 13 to a high of 32 ug/L, but most of the values are at the lower end of that range. You can tell this because the dot (in the case of the stick plot) and the median line (for box plots) are closer to the bottom than the top.

An example of a graph showing seasonal variation (1), a stick plot (2), and a box plot (3). The stick plot and box plots shown represent only the seasonal variation data (1) from May 15 through September 15.

 

Parameter
Abbreviation
Unit of Measure
Water Clarity (using Secchi disk)
Secchi
Inches (")
Total Phosphorus
TP
Micrograms per liter (ug/L) or parts per billion (ppb)
Total Nitrogen
TN
Micrograms per liter (ug/L) or parts per billion (ppb)
Total Chlorophyll
CHL
Micrograms per liter (ug/L) or parts per billion (ppb)
Inorganic Suspended Sediments
ISS
Milligrams per liter (mg/L) or parts per million (ppm)

The parameters measured by the Lakes of Missouri Volunteer Program, the abbreviations used in the data reports, and the units of measure that the numbers represent.

 

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The Lakes of Missouri Volunteer Program is operated by employees of the University of Missouri