Rapid publication-ready MS-Word tables for
one-way ANOVA
Abstract
Background: Statistical tables are an important component of data analysis and reports in biological sciences.
However, the traditional manual processes for computation and presentation of statistically significant results using
a letter-based algorithm are tedious and prone to errors.
Results: Based on the R language, we present two web-based software for individual and summary data, freely
available online, at http://shiny.stat.tamu.edu:3838/hassaad/Table_report1/ and http://shiny.stat.tamu.edu:3838/
hassaad/SumAOV1/, respectively. The software are capable of rapidly generating publication-ready tables containing
one-way analysis of variance (ANOVA) results. No download is required. Additionally, the software can perform
multiple comparisons of means using the Duncan, Student-Newman-Keuls, Tukey Kramer, and Fisher’s least
significant difference (LSD) tests. If the LSD test is selected, multiple methods (e.g., Bonferroni and Holm) are
available for adjusting p-values. Using the software, the procedures of ANOVA can be completed within seconds
using a web-browser, preferably Mozilla Firefox or Google Chrome, and a few mouse clicks. Furthermore, the
software can handle one-way ANOVA for summary data (i.e. sample size, mean, and SD or SEM per treatment
group) with post-hoc multiple comparisons among treatment means. To our awareness, none of the currently
available commercial (e.g., SPSS and SAS) or open-source software (e.g., R and Python) can perform such a rapid
task without advanced knowledge of the corresponding programming language.
Conclusions: Our new and user-friendly software to perform statistical analysis and generate publication-ready
MS-Word tables for one-way ANOVA are expected to facilitate research in agriculture, biomedicine, and other fields
of life sciences.
Keywords: Statistical analysis; Multiple comparisons; Online software; Computation; Biology; R; Shiny
Introduction
Statistical tables are ubiquitous in agricultural, biological,
and biomedical studies (Steel et al. 1997). An example is
shown in Table 1, reporting the effects of oral administration
of interferon tau (IFNT) on concentrations of
amino acids, glucose, lipids, and hormones in the plasma
of Zucker diabetic fatty (ZDF) rats (Tekwe et al. 2013).
Here, we focus on generating tables from one-way analysis
of variance (ANOVA) models where measurements are
summarized as mean ± SEM for each treatment group.
Typically, post-hoc test results are also included in these
tables using a letter-based algorithm (Piepho 2004) to
indicate which treatment groups are significantly different.
With this algorithm, means for treatments are assigned
letters (e.g., a, b, and c) to highlight significant differences.
Those means that are not significantly different are
assigned a common letter. In other words, two treatments
without a common letter are statistically significant at the
chosen level of significance (e.g., P ≤ 0.05 or ≤ 0.01). The
Tukey-Kramer (TK), Student-Newman-Keuls (SNK),
Fisher’s least significant difference (LSD), Duncan (DC),
and Bonferroni (BF) tests are among the most popular
multiple comparison procedures used in life science
research (Steel et al. 1997), including amino acid
biochemistry, nutrition, pharmacology, and physiology
(Wang et al. 2014a,b; Wu and Meininger 1997; Wu
1997).
Table 1 Effects of oral administration of IFNT on
concentrations of amino acids, glucose, lipids and
hormones in the plasma of ZDF rats
Metabolites or
hormones in plasma
Oral IFNT dose (μg/kg BW/day)
Adapted from Tekwe et al. (2013). Plasma samples were obtained from 12-week-old
rats. Values are the means ± SEM, n = 6 per treatment. a-bMeans in a row without a
common superscript letter differ (P < 0.05), as analyzed by one-way ANOVA.
In this paper, we introduce two software, freely available
online, at (http://shiny.stat.tamu.edu:3838/hassaad/Table_
report1/ and http://shiny.stat.tamu.edu:3838/hassaad/Sum
AOV1/) for one-way ANOVA. The software are capable,
within few clicks, of generating publication-ready MSWord
tables corresponding to multiple data sets, and of
exporting them to Microsoft Word or any RTF reader,
with all the post-hoc tests results being included therein.
The software can also handle situations where only summary
data are available (i.e., sample size, mean, and SD or
SEM per group), without the need to use the original individual
observations. We believe that our new method will
save biologists, and applied scientists in general, an ample
amount of time and avoid inputting, by hand, superscript
letters (see Table 1) derived from the appropriate statistical
tests. This offers a distinct advantage over the traditional
manual processes for computation and presentation of
results in tables that are not only tedious but are also
prone to errors.
Several software packages can perform one-way
ANOVA, followed by post-hoc analysis (e.g., R, SAS,
JMP, and SPSS). To our knowledge, none of them is capable
of exporting the multiple comparison results into
an RTF reader in a format similar to that of Table 1
without advanced knowledge of the corresponding programming
language. Also, SAS, SPSS and JMP are not
free. The main challenge lies in exporting the superscripts
used to summarize the significance results to an RTF
reader. A simple Google search of the terms “ANOVA
calculator” or “ANOVA from summary data” reveals many
free web-based programsa that can construct ANOVA
tables based either on original or summary data. Despite
their simple interface, these programs suffer from major
drawbacks. The majority cannot perform post-hoc analysis
of any kind. Additionally, none of them can export results
to an RTF reader in a publication-ready format, making
their usage by a broad community very unlikely. To overcome
these disadvantages, we wrote our software in the R
language (R core Team, 2014) and used the following
R packages: grifExtra (Auguie 2012), XLConnect (Mirai
Solutions GmbH 2014), agricolae (Mendiburu 2014), rtf
(Schaffer 2013), and shiny (Rstudio Inc 2013).
In the following sections, we introduce necessary background
materials for one-way ANOVA coupled with
multiple comparison techniques. The main goal is to
highlight some of the limitations of the statistical tests
included in the software. We also wanted to underline
the necessary assumptions required by one-way ANOVA
and emphasize that the software should be used only
when such assumptions are nearly satisfied. In addition,
we present several options to prepare the data for input
into the software. Different toy datasets can be downloaded
from the software webpage to be used throughout
the paper to illustrate the functionality of our software.
We also describe the different components of the software
and the steps required to generate the tables in MS Word.
Furthermore, we offer various tips and useful links to
cover more input and output scenarios. Concluding
remarks are given towards the end of this article.
Background and materials
1. One-way ANOVA
Here, we present a brief non-technical description of
one-way ANOVA and introduce few terms that will be
used throughout the rest of this paper. One-way ANOVA,
also known as single-factor ANOVA, involves the analysis
of data sampled from two or more numerical populations
(probability distributions). The characteristic that labels
the different populations is called the factor under study.
This factor variable can take different values known as
factor levels. For example, in a published study involving
dietary supplementation with 0, 0.5, 1, 2, and 4% monosodium
glutamate to young pigs (Rezaei et al. 2013), the
experiment consisted of one factor (i.e., monosodium
glutamate) with five different levels. Also, let us consider
an experiment to assess the effect of four brands
of gasoline automobile on engine operating efficiency
(measured in mpg). Here, the brand of gasoline is the
factor variable and it has four levels (the four brands).
The response variable is the engine operating efficiency.
One-way ANOVA assumes that the numerical populations
or probability distributions of each factor level
follow a normal distribution with a common variance,
and differ only with respect to their means. Therefore,
differences in the means reflect the effect of the essential
factor levels, and it is for this reason that ANOVA
focuses on the mean responses for the different factor
levels. If the factor has only two levels, ANOVA is equivalent
to an unpaired t-test comparing two group means.
One-way ANOVA usually proceeds in two steps. First, it
determines whether or not the factor level means are the
same using an overall test. Second, if the factor level
means differ, the researcher will conduct a follow-up
analysis, known-as post-hoc analysis, to examine how
they differ. Our software offers a variety of statistical
tests to perform pair-wise comparisons in the post-hoc
analysis step.