Hardy-Weinberg equilibrium calculator including analysis for ascertainment bias

Chi-sq Hardy-Weinberg equilibrium test calculator for biallelic markers (SNPs, indels etc), including analysis for ascertainment bias for dominant/recessive models (due to biological or technial causes)
Enter observed counts for each genotype, then click "Calculate". (Copyright TRG, SR, INMD, 2008)

If you use this web-tool please cite:
Santiago Rodriguez, Tom R. Gaunt and Ian N. M. Day.
Hardy-Weinberg Equilibrium Testing of Biological Ascertainment for Mendelian Randomization Studies.
American Journal of Epidemiology Advance Access published on January 6, 2009, DOI 10.1093/aje/kwn359.

Common homozygotes    Heterozygotes    Rare Homozygotes  

Results area - enter data above and click calculateinset

(all results rounded to 2 decimal places)

Chi-squared distribution (1 degree of freedom):

P value 0.05 0.01 0.005 0.001
Chi-squared 3.84 6.63 7.88 10.83


  • X2 refers to chi-squared
  • The X2 value indicates the difference between expected and observed values for genotype counts
  • The likelihood of observing these differences by chance can be determined from a X2 table (1 d.f.), a brief example of which is above
  • Ascertainment bias (biological or technical reasons) may cause gains or losses in observed counts. This calculator indicates the expected counts under HWE if gains or losses have occured in one genotype group (dominant/recessive model) in addition to the conventional analysis which distributes gains/losses across all three genotype groups


© 2008 TRG, SR, INMD.
No guarantees are made of the accuracy or completeness of this site, and no liability can be accepted for any losses resulting from its use.