Question

已知一组数据9,10,11,x,y的平均数为10,方差为2,求这组数据

Answer 1

由题意知,

9+10+11+x+y=10*5=50,即x+y=20,X=20-Y

又方差=（9-10）^2+(10-10)^2+(11-10)^2+(X-10)^2+(Y-10)^2=2*5=10,即(20-Y-10)^2+(Y-10)^2=8,

SO (Y-10)^2=4

SO Y=12,或Y=8

当Y=12时,X=8;当Y=8时,X=12,

SO 这组数据为8,9,10,11,12