STATISTICAL GRAPH
The title of each graph of the statistical study indicates the parents' variables (R or M & F) to which the correlations relate. Each point of the colored lines represents the correlations with the observational C variables of the children.
Likewise, the variables of unknown order, formed by the different groups of 1 to 10 values from the 70 IQ values of each parent and children variables, appear on the left-hand side of the graph. The criteria order of the groups of 1 to 10 values located on the right-hand side is the variable mentioned at the bottom of the graph.
Indeed, there is an almost instantaneous perception of the exactitude of the particular specification of the statistical study; each graph shows sixty coefficients of determination (r²) highlighting the global and underlying relations of the involved data set.
See the methodology of the statistical abstract for more details
STATISTICAL STUDY COMMENTS
1. General statistical significance
The considerable increase of the correlation for the estimation of homogenous groups is not due to the reduction of 68 to 5 or 4 degrees of freedom, since the estimation with non-homogenous groups, without previous rearrangement, has the same degrees of freedom and the correlation even lowers concerning the sample without grouping.
In general, the model of the genetic evolution of intelligence (Mendelian genetics – Conditional intelligence – Global Cognitive Theory) adjusts perfectly, showing an r² superior to 0.9 in several cases. Bearing in mind the tendency to increase the goodness of fit with the size of rearranged groups, we could assume it would be over 0,9 in almost all the cases for grander groups within a more significant sample.
2. Family - Intelligence of identical and non identical twins.
Family relationships are very interesting regarding genetics and intelligence, in fact, the whole EDI study is related to family characteristics.
Some research can be done regarding relations of identical twins, non identical twins, clones and even the effect of intelligence while selecting a partner or sexual selection.
Actually, we know that all C variables correspond to mono-environmental identical twin brothers, whereas W will only be a sibling; for that reason, sometimes they will look alike and others not so much.
It does not seem hard to imagine some interesting studies on these peculiar matters.
For instance, the selection of a partner as an auxiliary mechanism of evolution has been a paradigm since the first developments of the theory of evolution. Darwin himself wrote The Descent of Man and Selection in Relation to Sex (1871) introducing a new factor, sexual selection, through which females or males choose those with the most attractive qualities as their partner.
3. Significant comments on this particular graph
Similarity of variable C's behaviour in the 0r81-twin-brothers graph can be interpreted in the sense that the coefficients could correspond to identical twins whereas the W would only be a normal sibling since it has been generated with the data of the same parents.
This performance can be found on numerous occasions when the rearrangement criterion is one of the C variables.
In the case shown in the 0r82-identical-twins graph, W is used as the criterion of arrangement, and the behaviour is slightly different; it seems that the four variables correspond to identical twins. This is, of course, a particular case.
Actually, we know that all C variables correspond to mono-environmental identical twin brothers, whereas W will only be a sibling; for that reason, sometimes they will look alike and others not so much.
It does not seem hard to imagine some interesting studies on these peculiar matters.