This may sound silly, but it is actually true; researched and validated.
Did you know that iPhone is best held with right hand when making or answering a phone call? Do I hear why???
Well, a recent research has shown that holding your iPhone with left hand reduces the strength or signal to the phone. Although this is said to affect other phones too, the difference between left and right seems to be highly evident on iPhone than the others.
The results shown below is the research outcome, however, iPhone 7 is not part of the research.