Statistics part1 , Statistics part2
Outlier: An outlier is a very extreme value in data that differs significantly from other observations. and lies outside the overall distribution.
The reasons for existence of a outlier in a data is either measurement or variability.
what is the problem with outlier ?
As we know that outlier are extreme values in data that means it can impact mean, standard deviation and this will lead us to wrong analysis of data.
How to recognize an outlier in data ?
As we know that IQR has lower limit Q1 and upper limit 3*Q3 that means between 25% to 75% , we can easily avoid extreme values in data in IQR.
z-score = data values (observation) - mean of data / standard deviation.