0) 
[The references are to pages. The subject-matter of the Exercises given at 
the ends of the chapters has been indexed only when such exercises (or 
the answers thereto) give the constants for statistical tables in the text, 
or theoretical results of general interest ; in all such cases the number of 
the question cited is given. In the case of authors’ names, citations in 
the text are given first, followed by citations of the authors’ papers or 
books in the lists of references. ] 
ABruiTy, general, refs., 388. efficients of, 37-39; illusory or 
Accident, deaths from (law of small misleading, 48-51 ; total possible 
chances), 265-266. number of, for n attributes, 54-56 ; 
Achenwall, Gottfried, Abriss der case of complete independence, 
Staatswissenschaft, 2. 56-57 ; use of ordinary correlation- 
Ages, at death of certain women coefficient as measure of asso- 
(table), 78 ; of husband and wife ciation, 216-217; Pearson's co- 
(correlation), 159 ; diagram, 173 ; efficient based on normal corre- 
constants (qu. 3), 189. lation (refs.), 40, 333; refs., 15, 
Aggregate, of classes, 10-11. 39-40, 333. 
Agricultural labourers’ earnings. See Association, partial, generally, 42- 
Earnings. 59; the problem, 4243; total 
Agriculture, experiment, errors in, and partial, def., 44 ; arithmetical 
refs., 396. treatment, 44-48; testing, in 
Airy, Sir G. B., use of terms * error ignorance of third-order frequen- 
of mean square ”’ and ** modulus,” cies, 51-54 ; refs., 57. 
144. Refs., Theory of Errors of — examples: inoculation against 
Observation, 360. cholera, 31-32, 34-35, 383-384; 
Ammon, O., hair and eye-colour data deaths and occupation, 52-53; 
cited from, 61. deaf-mutism and imbecility, 32- 
Anderson, O., correlation difference 33; eye-colour of father and son, 
method, 198 ; refs., 208, 392. 33-34 ; eye-colour of grandparent, 
Annual value of dwelling-houses parent, and offspring, 46-48, 53— 
(table), 83; of estates in 1715, 54; colour and prickliness of 
table, 100 ; diagram, 101. Datura fruits, 36-37, 377-378; 
Arithmetic mean. See Mean, arith- defects in school children, 45-46. 
metic. Asymmetrical frequency-distribu- 
Array, def., 164; standard-devia- tions, 90-102; relative positions 
tion of, 177, 204-205, 236-237, in of mean, median, and mode in, 
normal correlation, 319-321. 121-122; diagrams, 113-114. See 
Association, generally, 25-59 ; def., also Frequency-distributions. 
28 ; degrees of, 29-39 ; testing by Asymmetry in frequency-distribu- 
comparison of percentages, 30-35 ; tions, measures of, 107, 149-150. 
constancy of difference from in- Attributes, theory of, generally, 
dependence values for the second- 1-59; def.,, 7; notation, 9-10, 
order frequencies, 35-36; co- 14-15 ; positive and negative, 10 ; 
4° 
J,