Aperception quotient
An aperception quotient was, in the field of 23rd century psychology, a relative means of measuring one's aperception, a figure that could potentially be used in determining the potential in one's abilities of possessing extrasensory perception. 

According to a readout on Dr. Elizabeth Dehner in 2265, she had an aperception quotient of 20/100, with an esper rating of 089. Her ratings were considered "better than average". 

Likewise, Gary Mitchell had an aperception quotient of 20/104, with an esper rating of 091. His ratings reached into the next level of "well above average". ()

fr:Quotient d'aperception
Psychology
Medical measurements