CONTENTS. 
CHAPTER VIL 
AVERAGES, 
18 
1. Necessity for quantitative definition of the characters of a 
frequency-distribution—2. Measures of position (averages) 
and of dispersion—3. The dimensions of an average the 
same as those of the variable—4. Desirable properties for 
an average to possess—5. The commoner forms of average— 
6-13. The arithmetic mean : its definition, calculation, and 
simpler properties—14-18. The median: its definition, 
calculation, and simpler properties—19-20. The mode : its 
definition and relation to mean and median—21. Summary 
comparison of the preceding forms of average—22-26. The 
geometric mean : its definition, simpler properties, and the 
cases in which it is specially applicable—27. The harmonic 
mean : its definition and calculation . . 106-132 
CHAPTER VIIL 
MEASURES OF DISPERSION, ETC, 
1. Inadequacy of the range as a measure of dispersion— 
2-13. The standard deviation : its definition, calculation, 
and properties—14-19. The mean deviation : its definition, 
calculation, and properties—20-24. The quartile deviation 
or semi-interquartile range—25. Measures of relative dis- 
genion 2 Measures of asymmetry or skewness—27-30. 
he method of grades or percentiles . : . 133-156 
CHAPTER IX. 
CORRELATION. 
1-3. The correlation table and its formation—4-5. The correlation 
surface—6-7. The general problem—=8-9. The line of means 
of rows and the line of means of columns: their relative 
positions in the case of independence and of varying degrees 
of correlation—10-14. The correlation-coefficient, the re- 
gressions, and the standard-deviations of arrays—15-16, 
Numerical caleulations— 17. Certain points to be re- 
membered in calculating and using the coefficient . . 157-190 
CHAPTER X, 
CORRELATION: ILLUSTRATIONS AND PRACTICAL 
METHODS. 
1. Necessity for careful choice of variables before proceeding to 
calculate 7—2-8. Illustration i.: Causation of pauperism— 
9-10. Illustration ii.: Inheritance of fertility—11-13. 
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