解：?$(2)s_{甲}^2=\frac {1}{10}×[(76 - 80)^2+(77 - 80)^2+(78 - 80)^2+(79 - 80)^2+(80 - 80)^2×2+(81 - 80)^2$?
?$+(83 - 80)^2×3]=5.8(\mathrm {mm}^2)；$?
?$ s_{乙}^2=\frac {1}{10}×[(75 - 80)^2+(76 - 80)^2×3+(79 - 80)^2+(80 - 80)^2+(81 - 80)^2+(83 - 80)^2+(86 - 80)^2$?
?$+(88 - 80)^2]=18.4(\mathrm {mm}^2)。$?
?$ $?因為?$5.8＜18.4，$?
所以甲供應(yīng)商供應(yīng)的蘋果大小更為整齊。
