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87
year and consequently it was found impossible to construct a
table shewing a weekly increase. The number of observations
is somewhat inadequate for the purpose but a glance at the
tables will shew that the weights indicate a steady if somewhat
irregular gain.
Type of Case. The weights of all young children who conformed
to the age shewn above were tabulated and con.
solidated and no selection whatever was made. Every recorded
weight was used in the construction of the tables.
Tables. The results of the enquiry are seen in the two
following Tables (No. 59 and No. 60), which shew, for boys and
girls respectively, their average weights at intervals of one
calendar month. There are some irregularities but these are
more or less inevitable when one has regard to the small
number of figures available and to the irregular intervals at
which the weights of children were recorded. An attempt
has been made to adjust these irregularities by means of
curves which are shewn in the diagrams. These curves probably
give results which are sufficiently accurate and practical
for the every-day work of the infant welfare centres. The
Tables shew, in addition, the number of observations made
each month, the weight in lbs, the standard deviation and the
co-efficient of variation for each set of observations. The
standard deviation is a statistical method of expressing how
closely rates of different babies at the same age approximate
to each other, and the co-efficient of variation is one hundred
times the standard deviation divided by the average weight.
In reading these mean (average) weights, the co-efficient of
variation will enable one to express the extent of variation
which can occur at any given age, e.g., at 15 months it can be
stated that 68.27 per cent. of all Woolwich malt infants will
be within the following limits of weight:—22.81 lbs. plus