I would like to average the weights which can be seen in the picture.
That means the calculation I want to make is : (50+65+70+68+70)/5
Do you know how to do that? (to specifically select the weights ones for every person using the household number and person number)
Seem you want to average the distinct weights per household:
SELECT AVG(Weight) FROM ( SELECT DISTINCT HouseHoldNumber, Weight -- maybe need to add TravelNumber or PersonNumber FROM tab ) AS dt