The $80\%$ or $4/5$th rule of thumb is a practical means of determining if a selection process has adverse impact against members of protected classes. Which statement best defines the $80\%$ or $4/5$th rule? A selection rate for

any race, sex or ethnic group which is less than $80\%$ or $4/5$th of the selection rate for the group with the highest selection rate.

female applicants that is $20\%$ of the selection rate for male applicants.

for an ethnic group that is $20\%$ of the selection rate for the ethnic group with the highest rate of selection.

any race, sex or ethnic group that is less than $60\%$ of the rate for the group with the highest selection rate.