A good example of that is resumes. A friend thought his resume was good but could not understand why he got turned down every time he applied for a job.

I picked an appropriate font, aligned things a bit in the layout and made good use of a couple of white space. 5min job, minor tweaks, zero copy changes.

Suddenly he got loads of positive replies to his applications.

The target crowd was not one aware of typography nor design knowledge. The volume of applications was also entering the realm of statistically significant.