vn] DISCUSSION OF THE DATA OF STATURE. 131 



and secondly of a tendency on the part of my corre- 

 spondents to record medium statures when they were 

 in doubt, whose effect would be to reduce the value of 

 the Prob. Error. The E.F.F. data in Table 12 run so 

 irregularly that I cannot interpret them with any 

 assurance. The value they give for Fraternal Eegression 

 certainly does not exceed ^, and therefore a correction, 

 amounting to no less than ^ of its amount, is required 

 to bring it to a parity with that derived from the 

 Special data (because ^ + ^ x \ = |). Hence it 

 might be argued, that the value of Eegression from 

 Mid-Parent to Son, which the E.F.F. data gave as |-, 

 ought to receive a similar correction. If so, it would 

 be raised to §- + -§■ = -§•; but I cannot believe this 

 high value to be correct. My first estimate made 

 from the E.F.F. data, was § , as already mentioned. If 

 this be adopted, the corrected value would be f , or -^ 

 instead of -§, which might possibly pass. Curiously 

 enough, this value of f for Eegression from Mid- Parent 

 to Son, coincides with the value of f for Eegression 

 from a single Parent to Son, which the direct observa- 

 tions showed (see page 99), but which owing to their 

 paucity and to the irregularity of the way in which 

 they ran, I rejected and still reject, at least for the 

 present. While sincerely desirous of obtaining a 

 revised value of average Filial Eegression from entirely 

 different and more accurate groups of data, the pro- 

 visional value already adopted of -| from Mid- Parent 

 to Son may be accepted as being near enough for the 

 present. It is impossible to revise one datum in the 



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