Which statement below is incorrect?
-The mean is not affected by the existence of an outlier.
-The median is not affected by the existence of an outlier.
-The standard deviation is affected by the existence of an outlier.
-The interquartile range is unaffected by the existence of an outlier.
-The mean is not affected by the existence of an outlier.
-The median is not affected by the existence of an outlier.
-The standard deviation is affected by the existence of an outlier.
-The interquartile range is unaffected by the existence of an outlier.