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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 14 Issue 2 (2009) pp 66-69

Graphical Representation of Analytical Data: Comparison of Different Analysts Using an Acid–Base Titration and Box-Whisker Plots

L. Escudero, L. Bustos,  S. Cerutti, L.D. Martinez, J.A. Gásquez*

Área de Química Analítica, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis. Chacabuco y Pedernera, 5700, TE/FAX 54-2652-425385. San Luis, Argentina,
Received May 6, 2007. Accepted  August 11, 2007.

Published online: 1 April 2009

Abstract. The statistical field of descriptive statistics involves the representation of experimental data sets using both numerical and graphical approaches. Concerning graphical representations, there are a great variety of categorized graphs, which can often identify expected and unexpected effects in the data more quickly and, sometimes, "better" than any other data analysis method; histograms (frequency distribution diagram) and scatterplots are good examples of these representations. Besides histograms, there are other ways to visually inspect a data set, and one that is popular is the box-whisker plot. This type of plot shows the spread of the data in terms of the median, the medians of the upper and lower halves of the data, and the spread between the medians of the upper and lower halves. The medians of the upper and lower halves of the data set are called the upper and lower fourth, respectively. These medians, also called the hinges of the box plot, are then used to create the box on the plot. Additionally, this kind of plot is useful to carry out detection of outliers, comparisons between different methodologies, inter-laboratory analyses, and analysts; among others. In the present work, we used box-whisker plots as graphical representations to compare analytical data from acid-base titrations with two different indicators.

Key Words: Computers in Chemistry; analytic chemistry; instrumental analysis; box plots; graphical approaches; outliers

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Issue date: April 1, 2009

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