Ch9

Scientific Writing and Communication, 2e Angelika H. Hofmann Copyright © 2014 by Oxford University Press

Chapter 9

Figures and Tables


Data Presentation

Present data in graphs when trends or relationships need to be revealed.

Prepare tables rather than graphs when it is important to give precise numbers.

Tables ? Figure ? Text ?


From Data to Results

• Prepare figures and tables with the reader in mind – place information where the reader expects to find it

• Design figures and tables to have strong visual impact

• Figures and tables should be able to stand on their own


Importance of Format

Different formats of data: Which do you prefer and why?

a) day 10, h (height) =45 cm; day 0, h=0 cm;

day 6, h=32 cm; day 2, h=10 cm; day 12, h=48cm; day 4, h=19cm

b) Time (days)

Height (cm)

0 0

2 10

4 19

6 32

8 38

10 45

12 48

Height (cm) Time (days)

0 0

10 2

19 4

32 6

38 8

45 10

48 12


Most common types

Photographs

Drawings and diagrams

Line graphs

Scatter plots

Bar graphs

Pie charts

Box plots

Figures


Most common: Line graphsBar graphs Scatter plotsPie charts

•Line graphs: for dynamic comparisons

•Bar graphs: when subdividing and comparing findings

•Scatter plots: to find a correlation for a collection of data

•Pie charts: to compare parts of a whole

Graphs


Readability• Large lettering and symbols• Easy-to-distinguish symbols• Uncluttered graphs

Emphasis• Highlight important information • Use different line weights:

Curves—darkest Letters in axis labels—less dark

Axes, tick marks, error bars, keys, curve labels—least dark

Figures: Readability and Emphasis


Sample Line Graph Format

3-4 curves ideal

3-4 curves ideal

Straight lines or smooth

curves

Straight lines or smooth

curvesKey on graph

or label curves directly

Key on graph or label curves directly

End at scale point; no

arrow

End at scale point; no

arrow

Reasonable scale

calibration

Reasonable scale

calibration

Y-axis reading upward

Y-axis reading upward

Include variable and

(units)

Include variable and

(units)

Tic marks on outsideTic marks on outside


Perc

ent w

eekl

y gr

owth

Y-axis label reads upwardY-axis label reads upward

Axis scale has proper spacing, font of numbers and label is large enough

Axis scale has proper spacing, font of numbers and label is large enough

Data sets are clearly distinguishable and labeled

Data sets are clearly distinguishable and labeled

Include error bars as needed

Include error bars as needed

Sample Bar Graph Format


Time (min)

Axis label show units in parenthesis(using SI abbreviations

Axis label show units in parenthesis(using SI abbreviations

Freq

uenc

y of

vis

its No box or

border around chart

No box or border around chart

Axis scale has proper spacing, tick marks are on the outside

Axis scale has proper spacing, tick marks are on the outside

Sample Scatter Plot

Axis stops at real number (no arrow)

Axis stops at real number (no arrow)


Graphs: Format

• Make each figure easy to read

• Differentiate points, lines, and curves well

• Label axes and scales well

• Do not mislead readers


Figure Legends

The figure legend should be a description of the figure content

•Different parts of figure legends• Brief title • Description of figure content• Definitions of symbols, line, or bar patterns• Abbreviations not defined earlier in the legend• For graphs, statistical information

Example

Figure 9: Western blot of protein Z deletion analogs. Lane 1, molecular weight standards. Lane 2, protein Z. Lane 3–6, ammonium sulfate pellets. Arrows indicate position of protein Z and its deletion analogs.


Tables

• Keep the structure as simple as possible

• Place familiar context on the left and new, important information on the right

• Design tables titles to identify the specific topic

• Label dependent variables in column headings and independent variables in row headings


Table Design

SpeciesPond 1 enclosurea

(number of individuals)*

Pond 2 enclosure(number of individuals)

Rana sylvatica 100 50

Ambystoma

maculatum 50 100Ambystoma opacum 10 10

Position table caption above the table

Position table caption above the table

Table 1 Initial stocking of R. sylvatica, A. maculatum, and A. opacum in pond enclosures

Headings include units in parenthesis where needed

Headings include units in parenthesis where needed

Standard errors of the mean are given in parentheses.* Footnote

Explanatory notesExplanatory notes

Provide a title that identifies the table topic

Provide a title that identifies the table topic


Statistical Analysis

Use statistical analysis to determine data trends and chance occurrence

Know the most common statistical terms and calculations

• Mean

• Range

• Deviation

• Variance

• Standard deviation

• 95% confidence interval


Standard Normal Distribution Curve

68.3%

95.4%

MeanMean

Standard deviationStandard deviation

Standard deviationStandard deviation


Statistical Significance

• Null hypothesis—assumes no difference among data sets

• To obtain measure of likely hood of rejecting null hypothesis, use statistical analysis:

• Student’s test• ANOVA• Non-parametric tests• Chi-square test• Regression analysis

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Ch9