104 THEORY OF STATISTICS.
during the years 1876-85. A sky completely, or almost completely,
 overcast at the time of observation is the most common,
a practically clear sky comes next, and intermediates are more
rare.
This form of distribution appears to be sometimes exhibited by
the percentages of offspring possessing a certain attribute when one
at least of the parents also possesses the attribute. The remarks
2000 |
! 1500
14000]
~
S 500
; Te
Dlr. a te A Ee. wr
Cloudiness
Fig. 19.—Frequency-distribution of Degrees of Cloudiness at Breslau
1876-85: 8653 observations. (Table XV.)
of Sir Francis Galton in Natural [nheritance suggest such a
form for the distribution of ¢consumptivity” amongst the offspring
 of consumptives, but the figures are not in a decisive shape.
Table XVI. gives the distribution for an analogous case, viz. the
TABLE XVI.—Showing the Percentages of Deaf-mutes among Children of
Parents one of whom at least was a Deaf-mute, for Marriages producing
Five Children or more. (Compiled from material in Marriages of the Deaf
tn America, ed. BE. A, Fay, Volta Bureau, Washington, 1898.)
Rl Nuiiber of 1! Peni Number of
Deaf-mutes. Families. 1.0 mutes. Fezailies.
0-20 220 60-80 55
20-40 20°5 80-100 15
40-60 12 —
Total "3

92%