解：?$(1)$?如下表:
?$\text {解: (2) } \bar x_{\text {甲 }}=9 \text { 環(huán) }, \bar x_{\text {乙 }}=9 \text { 環(huán) }, s_{\text {甲 }}^{2}=\frac{2}{3}, s_{\text {乙 }}^{2}=1,$?
∵?$\bar x_{\text {甲 }}=\bar x_{\text {乙 }}, s_{\text {甲 }}^{2}<s_{\text {乙 }}^{2},$?
∴?$\text { 甲與乙 }$?的平均成績(jī)相同, 但甲發(fā)揮得比乙穩(wěn)定.
