Data Screening

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Chapter 7 Data Screening
Tables, Figures, and Equations
From McCune, B. J. B. Grace. 2002. Analysis
of Ecological Communities. MjM Software Design,
Gleneden Beach, Oregon http//www.pcord.com
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Figure 7.1. Frequency distribution showing a
univariate outlier falling 5.5 standard
deviations above the mean.
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Table 7.1. Steps to detect, describe, and reduce
the influence of outliers.
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Figure 7.2. A bivariate outlier that is not a
univariate outlier for either of the two
variables Sp1 and Sp2.
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Table 7.2. Deviations of the mean distance to an
outlying sample unit from the average distance
among sample units, using five distance measures.
( based on artificial noiseless data set of
smooth species responses, with one SU disrupted
by anomalous values.)
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Figure 7.3. Frequency distribution of average
relative Euclidean distances to particular sample
units with a total of 25 sample units. The
sample unit represented by the rightmost bar is
3.2 standard deviations above the mean of the
average distances.