Height and weight measurements were used to construct age- and sex-standardized BMI z-scores
using CDC reference data from U.
Continuous outcome variables such as BMI z-scores
and height deflections were screened for outliers using the Box-Cox plot, while categorical variables were screened using frequency distributions.
These indices were expressed in terms of z-scores
, relative to the international WHO growth standards for school going children, and were later used to classify malnourished children.
Results: We calculated the Z-scores
of 'weight for height' (WfH), 'weight for age' (WfA) and 'height for age' (HfA) and found the values less than -2 for 8.
I then converted all scores to z-scores
using the formula (X-M)/SD, where X is the number of hits, and M and SD are the mean and standard deviation of the distribution of hits for all valid Ps.
In the last Statistical Sidebar, "Distribution of Scores Around the Mean and the Purpose of z-scores
," I explained how data might be distributed around a mean.
Statistically significant difference was found in bone mineral density z-scores
of moderate to severe compared to mild Cerebral Palsy group (p<0.
Presentation of z-scores
allows for normalized appraisals of the two worldwide data-sets in a comparative statistical framework (Campbell & Stanley, 1963).
Birthweight and birth length z-scores
were also classified according to the INTERGROWTH-21st criterion (12).
In the updated methodology, measures with potentially skewed distributions (percentage measures only) are instead scored with truncated z-scores
, instead of probit scores.
The children in the latter group had higher body mass index-for-age z-scores
(BMIz)--a measure of body fat in children.
sup] The Z-scores
were calculated as the body surface area (BSA)-adjusted mean coronary internal diameters established by de Zorzi et al .