Treatment of outliers/extremes in PLS
Posted: Wed Feb 08, 2006 11:38 am
Dear all,
one big advantage of PLS - in comparison with the covariance SEM - is that it requires no special distribution.
However, what is the best way to deal with outliers/extremes? A generally accepted statistical law is that you shouldn't base your results on outliers/extremes.
The background of my question is the following: I've one latent variable (formative) in my model. The indicators (ordinal scale) with the highest weights proved to be the ones which performed with very low medians in the descriptive analysis. An analysis with the stem-and-leaf plot in SPSS showed that exactly these indicators had many outliers and even extremes. Thus, the possibility exists that the weights are based on these outliers/extremes.
What would you recommend? Substitute the outliers/extremes with missing values or with the median? Or ignore completely the indicators which have outliers/extremes -- I personally would deny the last, as a formative construct is concerned and the deletion of indicators is always connected with a loss of content validity.
Thanks for your answers!
Heike Moses
one big advantage of PLS - in comparison with the covariance SEM - is that it requires no special distribution.
However, what is the best way to deal with outliers/extremes? A generally accepted statistical law is that you shouldn't base your results on outliers/extremes.
The background of my question is the following: I've one latent variable (formative) in my model. The indicators (ordinal scale) with the highest weights proved to be the ones which performed with very low medians in the descriptive analysis. An analysis with the stem-and-leaf plot in SPSS showed that exactly these indicators had many outliers and even extremes. Thus, the possibility exists that the weights are based on these outliers/extremes.
What would you recommend? Substitute the outliers/extremes with missing values or with the median? Or ignore completely the indicators which have outliers/extremes -- I personally would deny the last, as a formative construct is concerned and the deletion of indicators is always connected with a loss of content validity.
Thanks for your answers!
Heike Moses