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Outliers that differ significantly from the rest of the dataset [2] may be plotted as individual points beyond the whiskers on the box-plot. Box plots are non-parametric : they display variation in samples of a statistical population without making any assumptions of the underlying statistical distribution [ 3 ] (though Tukey's boxplot assumes ...
The modified Thompson Tau test is used to find one outlier at a time (largest value of δ is removed if it is an outlier). Meaning, if a data point is found to be an outlier, it is removed from the data set and the test is applied again with a new average and rejection region. This process is continued until no outliers remain in a data set.
The sample maximum and minimum are the least robust statistics: they are maximally sensitive to outliers.. This can either be an advantage or a drawback: if extreme values are real (not measurement errors), and of real consequence, as in applications of extreme value theory such as building dikes or financial loss, then outliers (as reflected in sample extrema) are important.
A boxplot may also indicate which observations, if any, might be considered outliers. Carpet plot : A two-dimensional plot that illustrates the interaction between two and three independent variables and one to three dependent variables. Comet plot : A two- or three-dimensional animated plot in which the data points are traced on the screen.
The idea behind Chauvenet's criterion finds a probability band that reasonably contains all n samples of a data set, centred on the mean of a normal distribution.By doing this, any data point from the n samples that lies outside this probability band can be considered an outlier, removed from the data set, and a new mean and standard deviation based on the remaining values and new sample size ...
The two boxes graphed on top of each other represent the middle 50% of the data, with the line separating the two boxes identifying the median data value and the top and bottom edges of the boxes represent the 75th and 25th percentile data points respectively. Box plots are non-parametric: they display variation in samples of a statistical ...
= + Boxplot Diagram with Outliers The lower fence is the "lower limit" and the upper fence is the "upper limit" of data, and any data lying outside these defined bounds can be considered an outlier. The fences provide a guideline by which to define an outlier , which may be defined in other ways.
[2] Grubbs's test detects one outlier at a time. This outlier is expunged from the dataset and the test is iterated until no outliers are detected. However, multiple iterations change the probabilities of detection, and the test should not be used for sample sizes of six or fewer since it frequently tags most of the points as outliers. [3]