Unable to carry out weight for hegiht zscore calculation

Hie guys,

Im still stuck here.

I believe there is a step I am missin or a rule I am failin to follow.

the error i am getting is:

calculation error: error in calculation for /
data/nutrition_statistics/score

Logic references instance (zscores) / zscore_list/zscore[gender =
/data/nutrition_statistics/height]/sd3neg which is not a valid question or
value.

What does this error mean?? and why am i being told gender and height are
invalid questions??

I have created a lookup table, inserted xml instance code in the form as i
understood it…

Can someone please guide me throuh to see where I am going wrong.

Eva