National Child Measurement Programme: Detailed Analysis of the ...

National Child Measurement Programme: Detailed Analysis of the 2007/08 Dataset 8were found for height (Table 3). Due to the way BMI is calculated (weight/height 2 ), rounding downof weight measures will decrease BMI, whilst rounding down of height measures will increase BMI.Rounding up of both measures would have the opposite effect. Because they have effects in oppositedirections, if both height and weight are rounded in the same direction this will to some extentreduce the impact on obesity prevalence.Table 3: Results of weighted linear regression between percentage of height measurementsrounded to whole number and half number against reported prevalence of obesity andoverweight & obesity for Reception and Year 6DependentvariableNumberof PCTsSlope (Betacoefficient)Standarderror ofBetaSignificance(p value)OddsRatiosCoefficient ofdetermination(R 2 )Reception obese 152 0.01 0.01 0.243 1.01 0.009Receptionoverweight &obese152 0.02 0.01 0.259 1.01 0.008Year 6 obese 152 0.00 0.01 0.758 1.00 0.001Year 6 overweight& obese152 0.01 0.02 0.646 1.00 0.001In order to control for the influence of rounding for both weight and height on each other, weightedregression analysis was repeated with both variables (Table 4)Table 4: Results of weighted linear regression between percentage of weight measurements andpercentage of height measurements rounded to whole number and half number against reportedprevalence of obesity and overweight & obesity for ReceptionDependentvariableWeightHeightSlope (Betacoefficient)Standarderror ofBetaSignificance(p value)OddsRatiosCoefficient ofdetermination(R 2 )Reception obeseWeightHeight-0.010.010.010.010.031*0.0980.991.010.040Receptionoverweight &obeseWeightHeight-0.040.030.010.01