Demographic and Health Surveys Methodology - Measure DHS

Statistics: Median Age at Contraceptive SterilizationDefinitionMedian age in years when women had contraceptive sterilization operation.A. Coverage: Women of all marital statuses who were sterilized at less than 40 years of age.B. Median type: Interpolated calculated median.CalculationA. Age at sterilization: Difference between date of sterilization operation and birth date of woman(in CMC format), truncated to single years of age.B. Numerators: Number of women within single age group categories. Women not sterilized are notincluded.C. Denominator is the number of women of all marital statuses who were sterilized at less than40 years of age.D. Numerators for each age group category are divided by the same denominator and multiplied by100 to obtain percentages.E. Medians are calculated from cumulated single year of age percent distributions of age atsterilization. Median is linearly interpolated between the age values by which 50 percent or moreof the women had been sterilized.Handling of Missing ValuesMissing values for age at sterilization have been imputed in the data set.Notes and ConsiderationsWomen who were sterilized at age 40 years or over are excluded from the calculation of the median tominimize problems of censoring.Since the difference between the date of sterilization and the respondent’s birth date is truncated to years,the difference is taken as including up to next completed year of age (the cumulated percentage forwomen with a difference of 29 years actually includes all women below 30 years of age at sterilization).Therefore an adjustment is made to the interpolated median by increasing the interpolated value by oneyear.Since the median is based only on women who have been sterilized by the time of the survey, the medianage is not calculated for periods of time of sterilization 10 years and more before the survey because ofcensoring (the oldest possible age in the data set would be 39 years at ten years prior and less for earliertime periods).Guide to DHS Statistics 52 Updated September 2006