Question

why is the 75th percentile least influenced by outliers

Answer 1

The interquartile range (IQR) is the difference between the upper (Q3) and lower (Q1) quartiles, and describes the middle 50% of values when ordered from lowest to highest.The IQR is often seen as a better measure of spread than the range as it is not affected by outliers.

Interquartile range is defined as the difference between the 25^th and 75^th percentile (also called the first and third quartile). Hence the interquartile range describes the middle 50% of observations. If the interquartile range is large it means that the middle 50% of observations are spaced wide apart. The important advantage of interquartile range is that it can be used as a measure of variability if the extreme values are not being recorded exactly (as in case of open-ended class intervals in the frequency distribution).[2] Other advantageous feature is that it is not affected by extreme values