▁ 0 . ▁This ▁implies ▁that ▁R AND ▁is ▁a ▁measure ▁ 1 ▁subset ▁of ▁the ▁set ▁of ▁all ▁infinite ▁sequences . ▁ ▁Every ▁random ▁sequence ▁is ▁normal . ▁ ▁There ▁is ▁a ▁construct ive ▁null ▁cover ▁of ▁R AND c . ▁This ▁means ▁that ▁all ▁effective ▁tests ▁for ▁random ness ▁( that ▁is , ▁ ▁construct ive ▁null ▁covers ) ▁are , ▁in ▁a ▁sense , ▁sub sum ed ▁by ▁this ▁universal ▁test ▁for ▁random ness , ▁since ▁any ▁sequence ▁that ▁passes ▁this ▁single ▁test ▁for ▁random ness ▁will ▁pass ▁all ▁tests ▁for ▁random ness . ▁( Martin - L ö f ▁ 1 9 6 6 ) ▁ ▁There ▁is ▁a ▁universal ▁construct ive ▁mart ing ale ▁d . ▁This ▁mart ing ale ▁is ▁universal ▁in ▁the ▁sense ▁that , ▁given ▁any ▁construct ive ▁mart ing ale ▁d , ▁if ▁d ▁succeed s ▁on ▁a ▁sequence , ▁then ▁d ▁succeed s ▁on ▁that ▁sequence ▁as ▁well . ▁Thus , ▁d ▁succeed s ▁on ▁every ▁sequence ▁in ▁R AND c ▁( but , ▁since ▁d ''' ▁is ▁construct ive , ▁it ▁succeed s ▁on ▁no ▁sequence ▁in ▁R AND ). ▁( S chn orr ▁ 1 9 7 1 ) ▁ ▁The ▁class ▁R AND ▁is ▁a ▁ ▁subset ▁of ▁Cant or ▁space , ▁where ▁ ▁refers ▁to ▁the ▁second ▁level ▁of ▁the ▁ar ithmet ical ▁hierarchy . ▁This ▁is ▁because ▁a ▁sequence ▁S ▁is ▁in ▁R AND ▁if ▁and ▁only ▁if ▁there ▁is ▁some ▁open ▁set ▁in ▁the ▁universal ▁effective ▁null