Linked Questions

94
votes
13answers
52k views

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 ...
73
votes
9answers
145k views

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 ...
44
votes
8answers
10k views

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, ...
27
votes
4answers
160k views

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 ...
6
votes
2answers
608 views

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 ...
5
votes
1answer
4k views

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 ...
1
vote
0answers
4k views

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 ...
12
votes
1answer
474 views

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: ...
5
votes
1answer
1k views

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 ...
0
votes
1answer
145 views

Difference between different methods of outlier determination?

how to calculate Cooks distance. How is this method of determining outlier different from the quartile method.
0
votes
0answers
89 views

When removing outlier is right? Removing techniques for outliers in R [duplicate]

I was searching outlier removal in R and I saw some comments related to almost never you should remove outlier from dataset. I wonder when we should remove outlier? I have a dataset consisting ...
0
votes
0answers
43 views

Pearson r Interpretation [duplicate]

Possible Duplicate: Magnitude of a relationship I have a set of data that has a Pearson correlation of .822 with sig. (1 tailed) of .001. I am not a statistics person but what exactly does that ...