6. (4) and the Median.
7. Diagram in illustration.
8–10. Average departure from the average, considered under the above heads, and under that of
11. (5) The (average of) Mean Square of Error,
12–14. The objects of taking averages.
15. Mr Galton's practical method of determining the average.
16, 17. No distinction between the average and the mean.
18–20. Distinction between what is necessary and what is experimental here.
21, 22. Theoretical defects in the determination of the ‘errors’.
23. Practical escape from these.