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In biological experiments one can get qualitative data like colour, health , intelligence,cure response of  drug etc which can be classified in praticular category,class or group.To analyze such qualitative data nonparametric test called chi-square test is performed. In genetic studies it is of great importance where it serves to test significance of overall deviation between the observed and expected frequencies.
Chi- square test was developed by prop. A.R. FISHER in 1870. KARL PEARSON improved FISHER's Chi-square test in its preasent day form in year 1900.
chi-square is derived from greek letter(CHI)

[[DEFINITION]]: Chi square test is the test of significance of overall deviation square in the observed and expected frequencies divided by expected frequencies.

[[Category:Biostatistics|Statistics]]