A simple weight average--look at the EXCEL programming to see how to do it
No of People Total weight weight in category
in category weight in category times weight
1 100 100 10000
1 110 110 12100
1 120 120 14400
1 130 130 16900
7 140 980 137200
1 150 150 22500
1 160 160 25600
total Weight 1750 Sum= =sum( 238700
total No people 13
Number avg= 134.6154 weight Average= 136.4
Alternately, the number average is the sum of the number fraction times the weight
while the weight average is the sume of the weight fraction times the weight
No of People Weight for weight of Number Weight No fraction times weight fraction
in category this category category Fraction Fraction weight times weight
1 100 100 0.076923 0.057142857 7.692307692 5.714286
1 110 110 0.076923 0.062857143 8.461538462 6.914286
1 120 120 0.076923 0.068571429 9.230769231 8.228571
1 130 130 0.076923 0.074285714 10 9.657143
7 140 980 0.538462 0.56 75.38461538 78.4
1 150 150 0.076923 0.085714286 11.53846154 12.85714
1 160 160 0.076923 0.091428571 12.30769231 14.62857
sums= 1 1 134.6153846 136.4
total Weight 1750
total No people 13
weight fraction
times weight