Because of the need to measure the IQ of people of varying ages, newer IQ tests base their evaluation of IQ on mental age alone deviation from the mean of the normal distribution giving extra points...

Because of the need to measure the IQ of people of varying ages, newer IQ tests base their evaluation of IQ on

 mental age alone

 deviation from the mean of the normal distribution

 giving extra points for older people to compensate for their slower processing times

all of these

or none of these