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The Mechanics of Scientific Writing
W.S. Warner, Ph.D.
Day 1 Analysis and Structure
Day 2 IMRAD and Argue
Day 3 Tables, Figures, Citation, Punctuation
Day 4 Clarity and Cohesion
Day 5 Concision & Precision
Program Day 1
Analysis –critical thinking from note taking to brainstorming
Structure –outlining: analytical, comparison & contrast, argumentative
Day 2
IMRAD – standard components of a publishable research manuscript
Argue – how to argue and develop a thesis statement
Day 3
Tables and Figures – how to make your writing understood
Citation –how to reference your sources.
Punctuation – how to make your writing accurate
Day 4
Clarity – six principles of clear writing
Cohesion – how to make your writing fluid
Day 5
Concision & Precision – how to make your writing tight and right
Review
Tables & Figures to compare & contrast
1. When to use a table or figure
2. Components of tables and figures
3. Design tips
Which format:
• Text – Not all analyses or results warrant a Table or Figure
– State simple results in text (data parenthetical)
In 2011, political prisoners in Libya increased significantly (125 p<0.001).
Seed germination was higher for plants in shallow-tilled soil (53 +/- 6 seeds) than for those in conventional plowed fields (14 +/- 3 seeds, t=11.2, p<0.001).
Text, Table or Figure?
Table or Figure?
– Clearer and more concise than text – Supplement not duplicate text – Time consuming to prepare
• Tables: compare numerical values and summarize data – Number of subjects – Means – Standard deviations
• Figures: show trends or patterns of relationship – Graphs & diagrams – Photos & drawings – Schematics & maps
How to refer to Tables and Figures • From the text
– All Tables and Figures must be referred to – Number sequentially (1, 2, 3, etc.) – Focus on data point, relationship, trend – Refer parenthetically
In 2010, murder per capita was lowest in rural areas (Table 4), which supports Smith’s (2001 ) 15-year trend of rural crime (Fig. 7).
• Do not simply direct the reader Table 1 shows the summary results for genetic variation of trout.
• Abbreviation – "Figure" abbreviated "Fig.“ – "Table" not abbreviated – Both spelled out in titles
• Figure 1: Economic growth (1969-2010)… • Table 1: Comparison of GPD…
Placement of Figures and Tables
• Consider your reader – Readability is vital
– Near first reference
– Do not interrupt flow
• May be embedded in text, but – Avoid breaking text into small blocks
– Better to have Fig. and Tables on their own pages
– End of Results or Discussion (for IMRAD), or appendix
The Anatomy of a Table
Table Structure 1. Title above the table
2. Units in column headings
3. Lines separate title, headings, data
4. Footnotes clarify – statistical differences
– data source (citation)
Descriptive Titles • Placement – think of the reader
• Lead the reader • Read a table; read top down - above Tables • Look at a figure; look up - beneath Figures
• Clear and complete • results • context: relationship displayed or treatment applied • location (ONLY if a field experiment) • explanation if needed to interpret results (e.g. footnotes) • sample sizes and statistical tests as they apply.
Figure 1. Height frequency (%) of White Pines (Pinus strobus) in the UMB Arboretum, Ås, Norway, before and after the 2010 ice storm. Before, n=137, after, n=133. Four trees fell during the storm and were excluded from post-storm survey.
• Do not restate the axis labels with "versus“ Figure 1: Poverty versus literacy.
Title Components
Data set changes mind set 1. Count 2. Comparison 3. Divisor
Murder Rates in EU Nations, 2010 (Homicides per 100,000 population)
Murder Rates in EU Nations, 2010 (Homicides per 100,000 population) US Public Health Care Expenditures, Per Capita: 1975-2004 (1999 dollars) US Public Health Care Expenditures, Per Capita: 1975-2004 (1999 dollars) State Voter Turnout Rates, Presidential Elections: 1992-2008 (Votes
cast/voting age population) State Voter Turnout Rates, Presidential Elections: 1992-2008 (Votes
cast/voting age population)
Divisor Rates, ratios, and per capita usually more meaningful than aggregate totals
Chicago 703 Detroit 43.0
New York 633 Chicago 25.6
Detroit 430 Philadelphia 23.3
Los Angeles 426 Dallas 23.1
Philadelphia 338 Phoenix 15.1
Houston 254 Houston 14.1
Dallas 252 Los Angeles 11.8
Phoenix 185 New York 8.6
San Antonio 89 San Antonio 8.1
San Diego 42 San Diego 3.5
source: Bureau of Justice Statistics: http://www.ojp.usdoj.gov/bjs/data/cities92.wk1
1a: Murders* in Ten Largest
US Cities, 1998
1b: Murder Rates* in Ten
Largest US Cities, 1998
*Murder and non-negligent
manslaughter per 100,000 population
*Murder and non-negligent
manslaughter
Sort data on the most
meaningful variable
Percent of 9-year-olds who
watch more than 5 hours of
television per weekday
Percent of 9-year-olds who
watch more than 5 hours of
televison per weekday
Canada 14.9 United States 21.5
Denmark 6.0 Spain 17.5
Finland 6.1 Canada 14.9
France 5.5 Netherlands 12.6
Germany 4.4 Ireland 11.8
Ireland 11.8 Italy 9.2
Italy 9.2 Finland 6.1
Netherlands 12.6 Denmark 6.0
Spain 17.5 France 5.5
Sweden 4.7 Sweden 4.7
United States 21.5 Germany 4.4
8a. Youth Television Watching
Source: Uri Bronfenburger, et. al. The State of Americans (New York: The Free Press, 1996); qtd. In
8b. Youth Television Watching
William Bennett, The Index of Leading Cultural Indicators (New York: Broadway Books, 1999), p. 230
If you are reading this table correctly, I’d be very surprised.
Good examples of bad
The Anatomy of a Line Graph illustrate disparities, illuminate trends
particularly over time
Anatomy of a Bar Graph illustrates disparities, illuminates trends,
highlights comparisons
Bar Graph Compares single variable (Y) among groups (X )
• Title describes – Variable measured (Y) – Treatment groups (X) – Sample size – Statistical test
• treatment groups (pH) specified • axis labels with units • error bars with sample number • statistical differences indicated
by lines over bars
Bar Graph Columns touch if X-axis is continuous
• measured single variable on the Y axis • groups (Habitat) on X axis • second group variable (year) different bar • key (within graph) defines bar fill • error bars show +1 SD above the mean • What’s wrong with the caption? • A, B, C, AC are not explained.
Frequency Histogram
Describes populations (size and age distributions)
Columns touch for continuous X-axis
• Y axis indicates relative frequencies (%). Could be absolute frequency (number of stems)
• X variable (ht) divided into categories • Sample size in the legend
Compound Figures
• Same format, different data A Harvested trees B Non-harvested trees
• Title identifies data set (A, B) • Text reads "...(Fig. 1b)"
Which variable goes where?
• It depends • dependent variable Y axis • independent variable X axis • tree height depends on age (age does not depend on height)
• Time is typically plotted as an independent variable. • No independent variable?
• inter-dependence: no difference which variable is on which axis • X,Y plot shows the relationship (rather than effect of one)
X
Y
More figures
Photographs
• Source cited in title
• Sufficient resolution to photocopy
Charts
Figure 9. Aerial photo of the study site ca. 1949 and in 1998 (inset) showing the regeneration of the forest. Photos courtesy of the USDA Field Office, Auburn, Maine.
• represent components of larger
group (tribal hierarchy)
• steps in a process (flow-chart)
• schematics of an instrument
Which to use?
Pie Charts indicate ratios, percentages
• Should rarely be used
• Difficult to discern size of pie slice relative to bar length
• 3-D pie charts add a visual distortion
Pie contests get messy
• Compare pies by adjusting the relative size
• Bad idea to use multiple pie charts to display more than one variable
• Made worse by "exploding" 3-D pies • If pie charts show percentages, make
sure they add up to 100 • Stay away from the fancy stuff
Bars
• 3-D bar uses more ink, for what?
• 2-D uses data labels (492, 363, 381, 173) rather than a 3-D y-axis scale
– reduces 6 numbers to 4
– adds precision
• Strict application of ink-to-data: present data as a table
Principle 1: Clarity
What’s wrong with this table?
• Value units not clear.
• Share = % ?
•Title should be more descriptive.
Good examples of bad
From bad to worse
Tips
• Less is more
– Simplify
– Half page/fig.
– Full page/compound fig.
• Highlight the important
• No pictures
Figuratively speaking Science not Art
• Color
– Can distinguish data sets – Photocopy will lose information – Never use color simply because it is pretty
• Bars twice as wide as gaps • Include
– Error bars (SD or SEM) when plotting means – Tick marks
• Major divide range of values • Minor subdivide in logical units
Figures don’t lie… UNICEF
• Purports gap between rich and poor countries is increasing
• Per capita GNP of wealthiest countries almost doubled ($12,000 to $26,000)
• Has middle or low income countries GNP doubled?
…but liars do figure. ODA (Official Development Assistance)
• Arrows show declining donation, growing wealth
• $18 drop not big gray arrow, but little line
• Relative to GNP, ODA has not changed.
Summary – check list
Refer to the point you want to make
Do not repeat information
Number sequentially (in chapters: Fig. 2.1, 2.2, 2.3)
Cite sources
Fig. 1 is taken from Smith (2004)
Table footnote: Data adapted from Smith et al. (2009)
Legend tells readers what they are looking at
Acid test
"Acid Test" for Tables and Figures
• Readability is critical – strive for simplicity
• Ask a colleague: Does it make sense?
• Must stand alone and be interpretable
• Must be understood by its title
Interactive figures http://www.ted.com/talks/lang/eng/hans_rosling_reveals_new_insights_on_poverty.html http://www.ted.com/talks/hans_rosling_shows_the_best_stats_you_ve_ever_seen.html
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