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

Describe law of likelihood, Law of likelihood : Within framework of the sta...

Law of likelihood : Within framework of the statistical model, a particular set of data supports one statistical hypothesis or assumption better than another if the likelihood of t

Calculate the standard deviation, Q. A toothpaste company want to know if i...

Q. A toothpaste company want to know if its new product increases the length of time in-between dentist visit to its user. The company sets a target for 180 days to determine if it

Statistcal computing flow charts for sums, 1. define statistical algorithms...

1. define statistical algorithms 2. write the flow charts for statistical algorithms for sums, squares and products. 3. write flow charts for statistical algorithms to generates ra

January 2015 Take-Home Assignment, 3. a. A researcher in Hong Kong computes...

3. a. A researcher in Hong Kong computes the correlation between the percentage of employee turnover and the local unemployment rate (also expressed as a percentage) over a 20-mont

Common cause failures (ccf), Common cause failures (CCF): Simultaneous fai...

Common cause failures (CCF): Simultaneous failures of the number of components due to a same reason. A reason can be external to the components, or it can be the single failure wh

Residual calculation, Regression line drawn as y= c+ 1075x ,when x was2, an...

Regression line drawn as y= c+ 1075x ,when x was2, and y was 239,given that y intercept was 11. Calculate the residual ?

Hosmer-lemeshow test, Hosmer-Lemeshow test is a goodness-of-fit test taken...

Hosmer-Lemeshow test is a goodness-of-fit test taken in use in logistic regression, particularly when there are regular covariates. Units are spitted into deciles based on predict

Minimum volume ellipsoid, Minimum volume ellipsoid is a term for ellipsoid...

Minimum volume ellipsoid is a term for ellipsoid of the minimum volume which covers some specified proportion of the set of multivariate data. It is commonly used to construct rob

Define percentile, Percentile : The set or group of divisions which produce...

Percentile : The set or group of divisions which produce exactly 100 equal parts in the series of continuous values, like blood pressure, height, weight, etc. Hence a person with b

Cumulative frequency distribution, The tabulation of a sample of observatio...

The tabulation of a sample of observations in terms of numbers falling below particular values. The empirical equivalent of the growing probability distribution. An example of such

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