Wikipedia tells me that:

“The average length of an adult male hand is 189 mm, while the average length of an adult female hand is 172 mm.”

As your users will be using your application with their hands, its important to keep in mind the size of the hand they will be using. There is clearly a difference between the right and left hand and even more clear is the size difference between male and female hands. Doing some research into the age and gender of your users can make an application’ flow increase.

Avarage hand length for males and females. [1]

Below is my analysis of how Apple kept hand size in mind while determining where to place certain elements of the settings.app

Please note that I used my own hand in the analysis, as my left hand is 18.5cm long.