Hardy-Weinberg Calculator

This tool computes Hardy-Weinberg equilibrium expectations and performs a chi-square test to assess deviations from random mating in diploid populations. It accepts either allele frequencies (p) and (q) or observed genotype counts (AA, Aa, aa) with total sample size N. Internally, it derives p and q as p = (2*AA + Aa)/(2N) and q = 1 - p, then calculates expected counts E_AA = p^2 N, E_Aa = 2pqN, E_aa = q^2 N. A chi-square statistic is computed as sum((O-E)^2/E) across genotype classes, with df = 1. Outputs include the observed counts, p, q, expected counts, the chi-square value, and the p-value. The tool also notes when any expected count is below 5, indicating that the chi-square approximation may be unreliable and suggesting data aggregation or exact testing where appropriate. Advanced users can provide allele frequencies directly to bypass count inputs and focus on equilibrium expectations. Results are suitable for documentation, QC pipelines, and teaching demonstrations.