Nonparametric data are analyzed by using Nonparametric Statistics. Again, it does not make sense to add together first and second place in a race - one does not get third place. Theoretically, as this represents ordinal data, this computation should not be done. IQ scores may be computed for a group of individuals. They will represent differences between individuals and the direction of those differences but they lack the property of indicating the amount of the differences.
Psychologists have no way of truly measuring and quantifying intelligence.
An individual with an IQ of 70 does not have exactly half of the intelligence of an individual with an IQ of 140. Therefore, IQ scales should theoretically be treated as ordinal data. In both of the above illustrations, the statement is make that they should be theoretically treated as ordinal data. This opens up the possibility for use of parametric statistical techniques with these data and the benefits associated with the use of techniques. Hopefully, the discussion above has helped you to understand a little better what the terms measurement and statistics mean.