From a New York Times article by Harvey Araton:
On a scale of 1 to 10, Andy Pettitte’s level of certitude seemed to be a 5. Halfway convinced he couldn’t grind out another year with the Yankees in New York, he opted for an unforced retirement in Houston to watch his children play sports and begin to figure out what to do with the rest of his life.
Perhaps the use of 1-to-10 scales should be retired, as well, because of the common misconception that 5 is halfway between 1 and 10. If you don't believe me, take a look:
Among the data reported, respondents were asked whether they think that divorce can never be justified (1), always be justifiable (10), or something in between. Seventeen percent of the 61,070 respondents for which a response was available selected 5 on the scale, but only eight percent selected 6 on the scale. The figure below shows that 5 was more popular than 6 even in countries whose populations leaned toward the 10 end of the scale.
It seems, then, that 5 serves as the ‘‘psychological mid-point’’ (see Rose, Munro, & Mishler 2004) of the 1-to-10 scale, which means that some respondents signal their neutrality by selecting a value closer to left end of the scale. This is not good.
Source: Harvey Araton. 2011. Saying It's Time, but Sounding Less Certain. NY Times.