Outliers - reasons for screening data, Advanced Statistics

Assignment Help:

Outliers - Reasons for Screening Data

Outliers are due to data entry errors, subject is not a member of the population that the sample is trying to represent, or the subject is really different. Statistical tests are quite sensitive to outliers so this problem should be addressed.

Univariate outliers are easy to detect (z-scores, box plots, histograms, etc.) standard scores larger than +/-3 are outliers (consider 4 is n>100 or 2.5 if n<10)

Multivariate outliers are difficult to detect. Mahalanobis distance is one powerful technique to use in this case (discussed later). This is evaluated as a chi-square statistic with degrees of freedom equal to number of variables in the analysis. A chi-sqaure statistic value that is significant beyond p<0.001 level determines outliers.

In most cases, it is ok to drop the value from the sample. One can also take steps to reduce the relative influence of outliers if the researcher decides to include the values in the analysis.


Related Discussions:- Outliers - reasons for screening data

Markov Model, How to estimate MLE for statistical anslysis using Markov Mod...

How to estimate MLE for statistical anslysis using Markov Model?

Categorical variable, Categorical variable : A variable which provides the ...

Categorical variable : A variable which provides the appropriate label of observation after the allocation to one of the several possible categories, for instance, the respiratory

Explain randomized response technique, Randomized response technique : The ...

Randomized response technique : The procedure for collecting the information on sensitive issues by means of the survey, in which an element of chance is introduced as to what quer

Minimization, Minimization is the method or technique for allocating patie...

Minimization is the method or technique for allocating patients to the treatments in clinical trials which is usually the acceptable alternative to random allocation. The procedur

Group divisible design, Group visible design is an arrangement of the v mn ...

Group visible design is an arrangement of the v mn treatments in b blocks such that: * Each block comprises k distinct treatments k5v; * Each treatment is replicated r number

Persson rootze ´n estimator, Persson Rootze ´n estimator  is an estimator f...

Persson Rootze ´n estimator  is an estimator for the parameters in the normal distribution when the sample is truncated so that all the observations under some fixed value C are re

Basic reproduction number, Basic reproduction number : A term used in the t...

Basic reproduction number : A term used in the theory of infectious diseases for the number of secondary cases which one case would generate in a completely susceptible population.

Descriptive statistics, how to describe association between quantitative an...

how to describe association between quantitative and categorical variables

Treatment allocation ratio, Treatment allocation ratio is the ratio of the...

Treatment allocation ratio is the ratio of the number of subjects allocated to the two treatments in a clinical trial. The equal allocation is most usual in practice, but it might

Partial least squares, Partial least squares is an alternative to the mult...

Partial least squares is an alternative to the multiple regressions which, in spite of using the original q explanatory variables directly, constructs the new set of k regressor v

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd