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

Unequal probability sampling, Unequal probability sampling is the sampling...

Unequal probability sampling is the sampling design in which the different sampling units in the population have different probabilities of being included in sample. The differing

Projection pursuit, Projection pursuit is a procedure for attaning a low-d...

Projection pursuit is a procedure for attaning a low-dimensional (usually two-dimensional) representation of the multivariate data, which will be particularly useful in revealing

Hirap, #q A paper mill products two grade of paper viz., X & Y. Because of ...

#q A paper mill products two grade of paper viz., X & Y. Because of raw material restriction, it cannot produce more than 400 tons of grade X paper & 300 tons of grade Y paper in a

Explain maternal mortality, Maternal mortality : The maternal death is the ...

Maternal mortality : The maternal death is the death of a woman while pregnant, delivering a baby or within 42 days of the termination of pregnancy, from any reason related to or a

Contour plot, Contour plot : A topographical map drawn from data comprising...

Contour plot : A topographical map drawn from data comprising observations on the three variables. One variable is represented on horizontal axis and the second variable is represe

Cauchy distribution, Cauchy distribution : The probability distribution, f ...

Cauchy distribution : The probability distribution, f (x), can be given as follows   where α is the position of the parameter (median) and the beta β a scale parameter. Moments

Explain kendall''s tau statistics, Kendall's tau statistics : The measures ...

Kendall's tau statistics : The measures of the correlation between the two sets of rankings. Kendall's tau itself (τ) is the rank correlation coefficient based on number of inversi

Explain isobologram., Isobologram  is a diagram used to characterize the in...

Isobologram  is a diagram used to characterize the interactions among jointly administered drugs or the chemicals. The contour of the constant response (that is the isobole), which

Data squashing, An approach to decrease the size of very large data sets in...

An approach to decrease the size of very large data sets in which the data are first 'binned' and then statistics such as the mean and variance/covariance are calculated on each bi

Mba, Mention the characteristics of Statistics. Explain any two application...

Mention the characteristics of Statistics. Explain any two applications of Statistics.

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