Excluding cases and controls with haplogroups other than the common five, left us with a sub-group of individuals effectively matched for haplogroup background consisting of 140 cases and 607 controls.
Cases that are poorly matched for genetic background may lead to false positives in association studies.
Therefore, child, adolescent and adult groups were well matched for educational background and socioeconomic status.
Different people participated in each of the workshops, but they were matched for disciplinary background and from the same institutions.
Nine external control populations, matched for Caucasian background, served to test for association of KCNE3 variants with tinnitus susceptibility ([ 22- 25], PharmGKB, dbSNP, HapMap-CEU and HapMap-TSI populations).
The two groups from WNY and Gomel were well matched for ethnic background, age, extent of disease (tumour size, nodal involvement, stage), tumour histology, grade and ER status.
All were recruited from the same academically selective secondary school in North London and were well matched for educational background and socioeconomic status.
We were able to compare the genomic abnormalities in the Belarussian cancers to those in similar tumours from a nonexposed area that were well matched for ethnic background, age, tumour characteristics, and extent of disease.
However, population stratification differences between case and control samples can give rise to both type I and II errors if case and control samples are not well matched for ethnic background.
If the cases and controls are not very well matched for local genetic background, the study can produce false-positive or false-negative results [ 7, 11, 13].
