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Example of a boxplot for the variable Age

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					           Example of a boxplot for the variable Age




The box represents the interquartile range.

The line across the box indicates the median.

The "whiskers" are lines that extend from the box to the highest
and lowest values, excluding outliers.

The circles above our upper whisker represent the outliers.

The location of the box between the whiskers tells us how the
data are distributed. If the box is in the middle of the whiskers,
the data are probably more evenly distributed.

If the box is closer to the lower whisker, the data are probably
skewed towards the lower end of the scale. If the box is closer to
the upper whisker, the data are probably skewed towards the
higher end of the scale.
              Example of a histogram




Example of a horizontal bar graph or bar chart
Using the correct scale in line graphs

When drawing a line, it is important that you use the correct scale.
Otherwise, the line's shape can give readers the wrong impression
about the data. Compare Figure 3 with Figure 4:

Figure 3.   Number of guilty crime offenders, Grishamville




Figure 4. Number of guilty crime offenders, Grishamville




Using a scale of 350 to 430 (Figure 3) focuses on a small
range of values.

It does not accurately depict the trend in guilty crime
offenders between January and May since it exaggerates
that trend and does not relate it to the bigger picture.

However, choosing a scale of 0 to 450 (Figure 4) better
displays how small the decline in the number of guilty
crime offenders really was.
A multiple line graph can effectively compare similar items over the
same period of time (Figure 5).

Figure 5. Cell phone use in Anytowne, 1996 to 2002




Figure 5 is an example of a very good graph.

The message is clearly stated in the title, and each of the line
graphs is properly labelled.

It is easy to see from this graph that the total cell phone use has
been rising steadily since 1996, except for a two-year period (1999
and 2000) where the numbers drop slightly.

The pattern of use for women and men is similar.

In summary, line graphs

      show specific values of data well
      reveal trends and relationships between data
      compare trends in different groups of a variable
     Focus on Your Data!
Keep Graphics Clean and Simple

                No!




            A lot Better!
Your job is to communicate clearly and directly with
your audience. Work to eliminate anything that
distracts from this.

Be sure you plot the relationship you want to show. If
you want to see the change in population through time,
the X-axis should be time and the Y-axis should be
population. Nothing else makes sense.

In the above example, only the two lines show your
data. The axes give the reader a sense of the range of
your data.
    Presenting data...the good and the bad - an example of
    a good and bad table.

binding          Energy (eV)                  Intensity (Counts)

                    275.0                              4311
                    275.1                              4366
                    275.2                              4380
                    275.3                              4436
                    275.4                              4578
                    275.5                              4673
                    275.6                              4684
                    275.7                              5191
                    275.8                              5371
                    275.9                              5453

    Table 3. XPS Intensities for Binding Energy of 275 - 276 eV.

    How many problems can you find with this table ?

                 datapoint binding intensity
                 number    energy


                                     1 275.00002                  4311

                                     2    275.100030           4366.0000




                                     3 275.20001                    4380

                                     4 275.30001                    4436

                                     5 275.40002                     4578

                                 6       275.50002                   4673

                                     7 275.60003                      4684

                                     8 275.70001                         5191

                                     9 275.80001                          5371

                                 10 275.90002                             5453

    Table III. Data points collected from the Shimadzu 270 (lab part 3B).
Example of a good and bad figure

How many problems can you find with the bottom
figure?




              Figure 1. XPS data for CxPFOS




    Chart A. The spectrum observed for group #6, sample
    "A".
Some additional tips for preparing figures and tables:

   All graph axes require labels that include
    both the variable name and units.

   Axes should use reasonable scales to clearly
    show the data and have labeled tic marks.
    The axis labels do not need to show the full
    number of significant figures.

   Table  columns should specify the units
    employed under each heading.

Use the results section to explain the purpose of
every figure, schemes, equation and table.

Published research results never include orphan
data, that is, information that is not explained or
put into context by the written text. This is also
a good rule to follow in lab reports.

When referring to a figure, table, or equation,
use its number in the text, for example:

A plateau was observed at reduced pressures
greater than 0.1, as indicated in Table 1.

				
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posted:8/3/2011
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Jun Wang Jun Wang Dr
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