Réponse :
bonsoir
moyenne
20×2+27.5×5+32.5×12+37.5×9+42.5×6=1160
1160÷34=34.12
20×181+27.5×470+32.5×830+37.5×654+42.5×160=74845
74845÷2295=32.61
variance 1/34(2(20-34.12)²+5(27.5-34.12)²+12(32.5-34.12)²+9(37.5-34.12)²+6(42.5-34.12)²)≈34.52
écart type =√34.52≈5.88
variance 1/2(295(20-32.61)²+470(27.5-32.61)²+830(32.5-32.61)²+654(37.5-32.61)²+160(42.5-32.61)²)≈45239.87
écart type √45239.87≈212.70
coef de variation
5.88/34.12×100=17.23
212.7/32.61×100=652.25
Explications étape par étape