The random sample was stratified for province and speciality and represents a sampling fraction of 9.2%.
This sample was stratified using LiDAR height and stocking density (nine strata).
Results were similar when the sample was stratified by twin pair, so that a single genetic marker is unlikely to explain the relation among depression, APOE, and dementia.
FINDINGS: When the sample was stratified for cumulative use, there was evidence of a linear relationship between cannabis use and FEV1/VC (P < 0.05).
The study sample was stratified by carotid intima media thickness (IMT) and ARIC field center; thus, all analyses were weighted by these factors.
Diabetes diagnoses were determined in the laboratory and ED, and the sample was stratified by age (>/<40 years).
The sample was stratified on geographic location and HIV caseload.
The sample was stratified for age and gender according to the characteristics of the general population of the Netherlands.
The sample was stratified by habitat and insects were randomly taken from selected houses from each strata.
The sample was stratified by age, gender, residence and province.
The sample was stratified according to birth cohort and sex.
