12 questions linked to/from Is there a simple way of detecting outliers?
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### What is the best way to identify outliers in multivariate data?

Suppose I have a large set of multivariate data with at least three variables. How can I find the outliers? Pairwise scatterplots won't work as it is possible for an outlier to exist in 3 dimensions ...
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### How should outliers be dealt with in linear regression analysis?

Often times a statistical analyst is handed a set dataset and asked to fit a model using a technique such as linear regression. Very frequently the dataset is accompanied with a disclaimer similar to ...
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### Rigorous definition of an outlier?

People often talk about dealing with outliers in statistics. The thing that bothers me about this is that, as far as I can tell, the definition of an outlier is completely subjective. For example, ...
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### Detecting outliers using standard deviations

Following my question here, I am wondering if there are strong views for or against the use of standard deviation to detect outliers (e.g. any datapoint that is more than 2 standard deviation is an ...
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### How to judge if a datapoint deviates substantially from the norm

This is Statistics 101, but I'm not a statistician and so can't seem to find the right technical jargon to google. My company collects data at discrete points through time. Today's datapoint is ...
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### Test for bivariate outliers

I have been given a set of data points $(x_i,y_i)$. I have to plot a scatter plot and determine if there are any outliers. But I haven't been taught a method to measure which data point is an outlier ...
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### threshold based on mean and standard deviation

I have a time series of 70000 data points. I want to separate samples of this time series which have very large values as compared to the time series. How can i threshold sample to separate. What i ...
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### How to find the sample points that have statistically meaningful large outlier ratios between two values of the point?

As an example application, consider following two properties of Stack Overflow users: reputation and profile view counts. It is expected that for most users those two values will be proportional: ...
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### statistical handling of lab values below limit of quantitation (BLQ)

There were several samples BLQ because of the lower limit of quantitation (LLQ) of the method, e.g. 5 ng/ml or less. Using the statistical program PRISM6 I marked these values together with the ...
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### Difference between different methods of outlier determination?

how to calculate Cooks distance. How is this method of determining outlier different from the quartile method.