数据分组 | \(\left\lbrack 12{.}5{,}15{.}5 \right)\) | \(\left\lbrack 15{.}5{,}18{.}5 \right)\) | \(\left\lbrack 18{.}5{,}21{.}5 \right)\) | \(\left\lbrack 21{.}5{,}24{.}5 \right)\) | \(\left\lbrack 24{.}5{,}27{.}5 \right)\) | \(\left\lbrack 27{.}5{,}30{.}5 \right)\) | \(\left\lbrack 30{.}5{,}33{.}5 \right)\) |