topic Outliers in skewed data in SAS Data Science

Outliers in skewed data

Srihari40 — Fri, 16 Jun 2017 09:48:09 GMT

Hi All,

Just wondering if there are ways we can find outliers in skewed(left or right) data? Just wondering if the tranformation of data(say log transformation and there by making data normal) helps in finding outliers?

Thanks,

Srihari

Re: Outliers in skewed data

frupaul — Fri, 16 Jun 2017 12:43:09 GMT

A number of plots, easily done on SAS Enterprise guide and base SAS, will help you spot outliers. Boxplots in particular and scatter plots.

However, to spot outliers on a Enterprise Miners, use the explore option to explore the distribution of the variables. Then by increasing the number of bins of the histogram to say 100, you will be able to spot outliers

Hope this helps,

Paul

Re: Outliers in skewed data

Srihari40 — Fri, 16 Jun 2017 16:05:03 GMT

Hi, Thanks for the reply. I dont use Enterprise miner. Box plot is perfect if the data has normal distribution not sure if it is right tool for skewed data. Wondering if transformation of data might help.

Thanks,

Srihari

Re: Outliers in skewed data

ballardw — Fri, 16 Jun 2017 16:39:31 GMT

@Srihari40 wrote:

Hi, Thanks for the reply. I dont use Enterprise miner. Box plot is perfect if the data has normal distribution not sure if it is right tool for skewed data. Wondering if transformation of data might help.

Thanks,

Srihari

I actually find box-plots MORE useful for skewed data. When the mean and median indicators don't align that shows one bit of the skewness. The lengths of IQR fences will also show the direction of skew and then the distribution of the extreme outliers.

Re: Outliers in skewed data

Srihari40 — Sat, 17 Jun 2017 11:33:12 GMT

Hi, Thanks for the reply.

I've attached the screen shot where I've attached skewed data variable and its transformed version. Wondering which one is better in figuring out the outliers?

Thanks,

Srihari