If you want to do your own range check, you can add a couple of memory tags '''InstrumentHigh''' and '''InstrumentLow'''.
mean(
if(isGood(if ({[.]1}>{[.]InstrumentHigh}||{[.]1}<{[.]InstrumentLow},qualifiedValue({[.]1},'bad',524,'Out of instrument range'),{[.]1})), {[.]1}, null),
if(isGood(if ({[.]2}>{[.]InstrumentHigh}||{[.]2}<{[.]InstrumentLow},qualifiedValue({[.]2},'bad',524,'Out of instrument range'),{[.]2})), {[.]2}, null),
if(isGood(if ({[.]3}>{[.]InstrumentHigh}||{[.]3}<{[.]InstrumentLow},qualifiedValue({[.]3},'bad',524,'Out of instrument range'),{[.]3})), {[.]3}, null),
if(isGood(if ({[.]4}>{[.]InstrumentHigh}||{[.]4}<{[.]InstrumentLow},qualifiedValue({[.]4},'bad',524,'Out of instrument range'),{[.]4})), {[.]4}, null),
if(isGood(if ({[.]5}>{[.]InstrumentHigh}||{[.]5}<{[.]InstrumentLow},qualifiedValue({[.]5},'bad',524,'Out of instrument range'),{[.]5})), {[.]5}, null),
if(isGood(if ({[.]6}>{[.]InstrumentHigh}||{[.]6}<{[.]InstrumentLow},qualifiedValue({[.]6},'bad',524,'Out of instrument range'),{[.]6})), {[.]6}, null),
if(isGood(if ({[.]7}>{[.]InstrumentHigh}||{[.]7}<{[.]InstrumentLow},qualifiedValue({[.]7},'bad',524,'Out of instrument range'),{[.]7})), {[.]7}, null),
if(isGood(if ({[.]8}>{[.]InstrumentHigh}||{[.]8}<{[.]InstrumentLow},qualifiedValue({[.]8},'bad',524,'Out of instrument range'),{[.]8})), {[.]8}, null),
if(isGood(if ({[.]9}>{[.]InstrumentHigh}||{[.]9}<{[.]InstrumentLow},qualifiedValue({[.]9},'bad',524,'Out of instrument range'),{[.]9})), {[.]9}, null),
if(isGood(if ({[.]10}>{[.]InstrumentHigh}||{[.]10}<{[.]InstrumentLow},qualifiedValue({[.]10},'bad',524,'Out of instrument range'),{[.]10})), {[.]10}, null)
)
If those instrument high/low limits are real, then you probably want those applied to all uses of the tag rather than just in calculating the mean.
If so, you could add a second set of derived tags '''Validated1''' etc, with an expression
if ({[.]1}>{[.]InstrumentHigh}||{[.]1}<{[.]InstrumentLow},qualifiedValue({[.]1},'bad',524,'Out of instrument range'),{[.]1})
If you reference Validated1
instead of 1
then you get the benefit of quality in displays and all calculations.