Kerfing a Bowed Stud

Wood studs are not perfect and never will be.  Neither will any other material, plant, etc. that is made in nature.  Through experience, science, and understanding, we learn how to manipulate natural materials to be suitable for our needs.  Trees, which have branches in many aspects of our lives (pun intended!), are a top renewable resource.  After centuries of harvesting tress, and thus lumber, to build shelters, etc., you would think our understanding of the material would be very thorough.  But as some say, it can be hard to see the forest through the trees.  In other words, sometimes you need to see the big picture.  Below is an example of an instance where the big picture reveals much more than what is in front of you 

It is common for carpenters to kerf a wood stud to remove a bow in the stud to allow for the wall finish to be flat.  Depending on the function of the wall, such as load bearing, the kerf in the stud may be reinforced with a section of 2x material lapped and fastened to the full height stud.  Regardless of how the stud is kerfed, reinforced, etc. the most important piece of knowledge involved is the function of the stud.  Knowing what the stud supports can result in an appropriate repair solution. 

These 2x6 studs have a kerf that leaves just over an inch of solid material. 

Now, back to that forest and tree stuff.  The worker who cut these studs could only see the bowed stud (tree) in front of him.  Had he looked at the big picture (forest), he might have realized that kerfing a first floor stud in a four story building might not be a good idea.  And yes, this wall does carry floor trusses from each floor above.