Statistics question

DATA: SUMMARIZING &

EXPLORING DATA

Characteristics of good figures Biol/Stat 2244 – Peter

Objectives

By the end of this module, you should be able to:

 Critically evaluate a figure to identify missing or

insufficient information;

 Label a figure appropriately;

 Identify relevant information for, and create an

appropriate figure caption;

 Understand when captions, legends/keys, and

titles are relevant.

Biol/Stat 2244 – Peter

Critically evaluate this figure

What things do you not understand or want to know

about to properly interpret this graph?

le n g th

treatment

Biol/Stat 2244 – Peter

What was lacking?

What things do you not understand or want to know

about to properly interpret this graph?

le n g th

treatment

Biol/Stat 2244 – Peter

units?

length

of what?

Vague…

what pH?

Informative axes titles help

Biol/Stat 2244 – Peter

• non-generic axis titles and tick labels • measurement units for quantitative variables • brief and efficient

le n g th

treatment

Figure captions provide context

Figure 1. Distributions of stem length of 30-day old sunflower seedlings (Helianthus

annus) following 20 daily treatments with water (control, n=20), or simulated acid rain

(SAR) solutions (n=15 for pH 3.5, n=22 for pH 2.0) in a greenhouse setting. SAR solutions

prepared from tapwater with 2 M sulfuric acid: 1 M nitric acid. Line over bars indicates

no significant differences. Kruskal-Wallis Test (p<0.0001) and Dunn’s post hoc test. Biol/Stat 2244 – Peter

Figure caption content

Biol/Stat 2244 – Peter

• elaboration of the variable(s) in the figure

Don’t explain the figure or study design;

provide details on the dataset!

• definitions of abbreviations on figure

• identification of statistical analysis symbolism

• who, what, when, where—as relevant or

necessary to interpretation

• sample sizes/replicates for comparative figures,

when not evident

When to include components

Biol/Stat 2244 – Peter

The nature of the ‘macro’ labels depends on the

format and presentation mode of a figure

In text formats: captions (below the figure), not

titles

• but…‘titles’ for multi-pane figures

Presentations: may have titles, but not captions

Symbolism must be purposeful (to distinguish

additional variables) and have a legend/key

Multi-pane figure

Graph title

for each

pane

Biol/Stat 2244 – Peter

Using colour or symbols

Legend/key

Biol/Stat 2244 – Peter