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In this table is given against each standard the number of boys with good, fair, or bad vision.
The columns are then added vertically and horizontally. The number that should fall in each group
if the distribution were uniform, that is if the distribution were the same in each standard as it is
in the total number, is then calculated by multiplying the sums of intersecting columns and dividing
by the total number. The quotient is then placed under the original figure (the second set of figures
in each square.) Thus the theoretical number for good vision in Standard I. is
for fair vision in Standard I.

The co-efficient of correlation exceeds its probable error in each case to such an extent that it
shows a definite relation to exist between acuity of vision and school attainments.
DENTAL CONDITIONS.
In the last two Reports attention was called at some length to the unsatisfactory dental condition
of the elementary school children, and it was shown that the more carefully they were examined
the greater the amount of destruction and disease found. Dental care is wanted at all ages.
Dr, Marion Hunter, in reporting on infants at the time of admission to school, gives instances of the
and so on. The difference of the theoretical and actual
numbers in each division is written down (the third number in each square). The result is squared,
so that all results are positive. Thus in Standard I 50 is the actual number of good vision, 70.56
the theoretical. The difference is 20.56 and the square of this 422.71. This is now divided by the
theoretical number 70.56 and the quotient, expressed to at least two places of decimals, is written
down in a column with the other similar results. The sum of these quotients then (x2) is found for
this particular example to be X4 = 88'38. This divided by the number of observations
that is
The co-efficient of correlation
And the probable error of this co-efficient is