data_anthro_for deposit.pdf
The WHO standards are available on the website of WHO (http://www.who.int/childgrowth/en/). You find there the software Anthro2005 for calculation of individual data (Anthro2005).
For calculating the z-scores of the new standards the LMS procedure is used. The principle is to get from a table for a certain age and sex 3 values (LMS) which are put into a formula For example WAZ = ((weight/M)^L-1)/(L*S)) e.g.:
Female, 9kg, 365 days => L = -0.2022, M = 8.9462, S = 0.12267
WAZ = ((9/M)^L-1)/(L*S) = ((9/8.9462)^-0.2022-1)/(-0.2022*0.12267) = 0.04885 Z-scores
On the WHO website you find only the LMS values for each month.
Wt L M S
9 -0.2022 8.9462 0.12267 0.048847178
To calculate the actual weight from the LSM statistics at any cut off point use the following formula:
wt = M * ((Z * S * L) +1)^(1/L)
Where Z = Zscore you are trying to obtain
This is the reverse of the formula to calculate WAZ etc.
And will give the standard to more decimal places for interpolation [purposes
I have taken 10 boys and 10 girls at 0.5 cm intervals from 60 to 110cm in height with weight for height mean at -1Z with SD or 1.0.
These are in the sheet WFH_Population.
For the simulation I have now added a random variable to the weight or the height in the POP_weight and the POP_height sheets.